Sunday, November 30, 2014

What *Wild* and Cheryl Strayed Taught Me about Tutoring

The Park on Parker Lane

Wild the movie opens this Friday, and I cannot WAIT to see it!

For those of you who might not be familiar with Wild the book, Wild is the story of a young woman whose life and and family have crumbled.  The author and main character of Wild, Cheryl Strayed, was 22 years old when she lost her mother.  In the wake of her mother’s death, her family life, including her marriage, dissolved.  Cheryl was like a planet without a sun, drifting aimlessly and dangerously, trying to find comfort through travel and sex and heroin.  She gradually descends to a bottom so dark that she feels blindly compelled to take action, to reclaim her life.  In a moment of pure genius or stupidity (or maybe both!), she decides to spend one summer walking the Pacific Crest Trail, a wilderness trail that runs along the American west coast, from Mexico to Canada.  The trailer for the movie knocked my socks off, and the book was excellent.  I’m thrilled to see the story brought to life on the big screen!

What I want to talk about today is a comment that Cheryl Strayed made during one of her many Wild book events.  She told us that when she started walking the Pacific Crest Trail, she didn’t know what she was doing.  She was woefully unprepared for the rigors of long-distance hiking.  But, she said, the trail taught her how to hike it.  The trail was her teacher.

That line.  The trail was her teacher.  Change one word, and that’s my story this year: the student was her teacher.  When I started tutoring, I figured I was in pretty good shape with my biology knowledge.  After all, I’d finished a neuroscience PhD program and spent four years working as a scientist in a world-class lab.  Surely I knew enough to be a good tutor.  And yet, looking back now, the amount of knowledge that I did not have is an avalanche compared to the snowflakes I had when I started tutoring.

But every student with whom I have worked has been my teacher.  Every student has taught me something about this work.  I’ve learned that every genetics student will ask me about three-point crosses.  Every high school chemistry student will ask me about dimensional analysis.  At a deeper level, I’ve learned when to go into full-on teacher mode and when to ask my student to solve problems.  I’ve learned more new-to-me biology and chemistry that I ever imagined I would as a tutor.  And I keep learning, because I realize now that I’ll always be learning more about these subjects.  I’ll always be asking myself, “How can I be a better teacher to my students?  How can I help them with their biggest challenges?  How can I provide genuine encouragement and helpful feedback?”

Truly, my students have been my best teachers.  Through our conversations, I’ve learned where my knowledge is lacking.  I’ve learned that I really enjoy teaching geometry, even though I still don’t consider myself a geometry tutor.  (That will probably change very soon.)  I’ve learned that I want to understand how to incorporate calculus into my chemistry knowledge—something I never did as an undergrad biochem major.  And I’ve learned that my tutoring is a collaborative process—my students and I co-create the experience.  We’re in it together, this learning thing.

It’s an incredible gift to be able to share one’s love for learning with other people.  With their generosity and grace, my students have given me so many blessings.  All I can really say is thank you.  I hope they know how special they are to me.

Turtle at the Pond    

PS  The photos in this post are from a park in my neighborhood, not the Pacific Crest Trail.  For now, I dream of hiking part of it myself.

Saturday, November 29, 2014

My Favorite Study Buddy

Lucy Likes to Learn

It never fails: I leave a textbook open on the floor, and Lucy wanders over to take a nap on it.

This week, I’m reading about chromosomal rearrangements, a genetics topic that I’d like to understand better.  A student asked me about Robertsonian translocations, and I had to admit to her that I’d never heard of them!  More about that phenomenon soon (or after finals).  The joy and challenge of my work is that there is always something new to learn, whether it’s translocations, or electrochemistry, or geometry (a subject I never thought I’d teach but that the universe seems to be implying I can and should).

That there is always room for growth and improvement makes me incredibly grateful for the work I get to do.  I’m grateful that I get to do something I love, that I get to do something helpful and valuable.  But mostly I’m grateful for all my lovely students.  They inspire me more than I can express.  I thank my lucky stars (and the internet) that they found me and that new students continue to find me.  I would not be able to do this work if it weren’t for them—for the financial support they provide (of course) and the way they make me want to do my best for them.   Being self-employed is great…except when it’s not.  My students remind me, again and again, what it means to keep trying and to see a commitment through to the end.

To any students who might be reading this, I wish you the best of luck with your upcoming finals.  Eyes on the prize and finish strong!  And if you need me, you know where to find me.

Saturday, October 25, 2014

Have you made a mistake lately? How fascinating!

It should come as no surprise to anyone that I love blog-hopping and finding new on-line goodies to read.  Tonight, I bumped into this post on the style blog Unfancy, and I want to share an excerpt from it:

Let me introduce you to one of my favorite people: Benjamin Zander. If I could pick anyone in the world to adopt as a grandfather, it would be this guy. He’s the renown [sic] conductor of the Boston Philharmonic + a wildly innovative, out-of-the-box thinker. He says:

“I actively train my students that when they make a mistake, they are to lift their arms in the air, smile, and say, ‘How fascinating!’ It is only when we make mistakes that we can really begin to notice what needs attention.”

How fascinating!  Isn’t that lovely?  Isn’t that a lovely way to think about your own learning as you work your way toward a greater understanding of yourself and your world?

This is what I hope for you: that you can find jewels of learning in your own mistakes and that you can find grace to forgive others for their mistakes.

Happy weekend, friends.

 

Friday, October 24, 2014

Come Meet the Austin Writing Shop!

Courtney at Our Table

This week and next week, Courtney and I will be hanging out at Café Crème to meet new students.  We’re excited to be out and about together, chatting with each other and students about writing projects.  You can see Courtney up there in the photo above, absorbed in her book at our Austin Writing Shop table.  We hatched an idea for a collaborative writing piece today, which I hope will make its way to the Austin Writing Shop’s content pages.

If you’re curious about our services and how we might help you with your writing project, now is a great time to meet us and learn about what we do.  Feel free to drop us an e-mail or catch us on Twitter for more info about exactly when we’ll be table-sitting at Café Crème.  (You can put in a request if you’d like to drink chai lattes with us!)

Happy writing!

Tuesday, September 30, 2014

We <3 Students!

Lu Loves Organic Chemistry

As September draws to a close, I’m inspired to reflect on the past month of working in Austin and how fortunate I have been.

Some of you may recall that my partner Paul and I relocated to Austin in August 2014.  We moved without “real jobs.”  Instead, our intention was to tutor full-time and make a living as freelancers.  We didn’t know how that plan would play out in the real marketplace; we just hoped that enough students would find us to make our lifestyle viable.

Paul and I had different ideas for our businesses.  Paul wanted to move his tutoring on-line so that he could continue to work with Texas A&M University students.  I planned to do a combination of in-person and on-line tutoring, working with students in the medium that worked best for them.  But regardless of the form, we were hoping for the best but preparing for the worst.  In my mind, the worst-case scenario was that we found no work in Austin and simply lived off of savings and/or credit cards while we hustled to find work.  I am happy to report that the results from our first month have been very, very good.

We know how much work we need in order to pay our bills.  To really make a freelance lifestyle work, you’ve got to be specific about your work and money goals.  To that end, it helps tremendously that Paul and I keep track of our spending.  We know exactly where our money goes.  That lets us see what we really value and how it fits into our vision of life.  (Wanna know what we love?  Food and our hydroponic garden are at the top of our list these days.)

In my first month of full-time tutoring, I’ve come really close to hitting my goal for weekly tutoring hours.  To be honest, this news comes as a delightful surprise to me.  I’m honored and humbled that so many of you have chosen to work with me, that you trust me to do this important work with you.  I’m inspired by your dedication to learning, to doing your best in challenging courses, to bouncing back after disappointing grades come back.  Being a student is hard work.  It’s my pleasure to join you on this journey, whether it’s for an hour or two or an entire semester of weekly tutoring sessions.

Thank you for everything, dear students.  I’m looking forward to the rest of the fall 2014 semester and continuing to do my best to help you do your best.  We <3 students, and we hope it shows.

Friday, September 19, 2014

The Learning Never Stops

“Lifelong learning” is a phrase you’ll hear educators say over and over again.  If you’ve been in school since the time you were five or six years old and have yet to live and work as a non-student, then the meaning of “lifelong learning” might be lost on you.  “Of course I’ve been a lifelong learner,” you say to yourself.  “I’ve been in school forever, and my job has been to learn.”

I too have spent most of my life in school, but this year I finally left academia to work as a private tutor.  I’m a freelancer now, which comes with a tremendous amount of freedom and no small amount of fear.  The most exciting thing about all this freedom is the near-constant opportunity to learn new things.  I thought I’d share some of those things with you, both as an illustration of lifelong learning as well as to document for myself how far I’ve come.

* My partner Tutor Paul developed our on-line tutoring platform earlier this year.  Paul is an engineer, which means that developing and utilizing technology is his bread and butter.  I am a biologist who does not have a natural affinity for new technology.  I’ve had to learn how to use the platform and get comfortable with the equipment set-up for on-line tutoring.  At this point, I think I’m mostly over the learning curve and have a much better handle on how to use the equipment.

* I have taught myself the course content for Texas A&M University’s Genetics 301 class.  Fun fact: I never took genetics as an undergrad.  Really, I wasn’t even interested in genetics until graduate school, when I learned how powerful it is.  So I arrived at genetics a bit older than my students, but I love teaching it.  My hope is to be one of the best genetics tutors in Austin.  It’s my favorite tutoring subject and it dovetails so nicely with molecular biology.

* I have been relearning general chemistry.  Gen chem is different now than it was when I took it.  That might be a function of my undergrad chemistry department; my professor friend tells me that their goal is to get students into organic chemistry after one semester of gen chem.  My reintroduction to general chemistry has given me new insights into the universe, new chances to experience wonder.  For example, now I better understand emission spectra and the idea of the electron as both a wave and a particle (just like light!).

* Finally, the most important thing I’ve had to learn is how to be in business for myself.  I’ve been really fortunate to have mentors who believed I could do it, who offered their insights and advice, who didn’t think I was crazy for wanting to be self-employed.  Without Paul and Jeremy, I don’t think I would have been brave enough to make the leap to full-time tutoring.  

* * *
What have you learned lately?

Friday, September 12, 2014

On-Line Genetics Tutoring, Sundays 3-4 PM

Hey, hey!

Starting this Sunday, September 14 from 3-4 PM, I’ll be holding an on-line group tutoring session for genetics students.  Right now, my sessions will be geared toward Texas A&M University Genetics 301 students because I’ve worked with those students, and I know they can benefit from my services.  But if you are taking a genetics class from a different university, you are welcome too!  I’ll answer student questions on a first-come, first-serve basis.

The cost of the session is $20 per person, and you can pay easily through PayPal or Venmo.  This is a great opportunity to work with a professional tutor and experience on-line tutoring, where you can get the help you want without leaving the house.

Here’s how it works:

* You’ll need a Google+ account and the Google Hang-outs plug-in, which you can find here.

* You’ll need a good internet connection and the ability to see video and hear audio.

* Connect with me on Google+ by finding me (Rose-Anne Meissner) and adding me to a circle.  Send me a message on Google+ to tell me you’re interested in the group session, and I’ll add you to the Hang-out.  Or send me a text message to tell me you are interested: 847-644-0782.

* You’ll be able to see me, hear me, and see me working on a virtual whiteboard.  I can e-mail anyone a copy of the session notes after we wrap up.

* Ask me questions and learn some genetics!

* Pay before or after the session.  But either way, please pay.  The only way I’m able to do this work is if students honor their end of the bargain.

Want to learn more about on-line tutoring?  Watch this video from my partner, Tutor Paul.

* * *

A word about payment:

“What if I don’t pay you for the group session?”

I can already hear some students thinking this question, cynical as it may sound.  A few encounters with no-pays does make a tutor weary.

First of all, if you are truly strapped for cash but want to attend the group session, contact me first.

But if you simply don’t pay, you won’t be invited back to the next session.  And if most students don’t pay, I’ll stop offering a group session.  I’m still available for group tutoring, but my normal group rate is much higher ($30/person) than the special Sunday session.

* * *

Happy learning!  I hope to see you on Hang-outs on Sunday.

 

Saturday, September 6, 2014

Already feeling overwhelmed by your semester?

Hey, guys!  This post is not a marketing pitch, I promise.  I just wanted to share another quote with you as we start to dive deep into the fall semester.  If you are already feeling overwhelmed by your semester (and if you are, I feel you, because that was always me in college), remember this:

“Obstacles are things a person sees when he takes his eyes off his goal.” ~E. Joseph Cossman

Also, how about a visual reminder about perseverance?

We All Get Hungry Sometimes

You’re welcome.  Now get back to studying.

Thursday, September 4, 2014

LESSON: Selection Pressure, Part Two

In this lesson, we’re going to pick up where my last lesson on selection pressure left off.  Here’s the link to the first lesson if you’d like to familiarize yourself with that first.

Today’s lesson focuses on how selection pressure changes allele frequencies over many generations.  Our sample problem is a follow-up to the scenario in my first lesson:

Despite your good work in Capitol City last time, the strange epidemic persisted and all individuals who lack Factor G are now sterile.  Individuals who lack Factor G are genotype gg; individuals who produce Factor G are GG or Gg and have normal levels of fertility.  How many generations will pass until the recessive g allele has a frequency of less than 1%?

In my last lesson, we figured out that when gg individuals cannot reproduce, the frequency of g drops from 0.3 in the parent population to 0.231 in the first generation after selection.  The simple formula for figuring out g’ if gg individuals are not reproducing is g’ = g/(1+g).

Here, g’ refers to the frequency of g in the next generation.  (And if you want to see the derivation of that simple formula, see my last lesson.)

If we do the math, we see that after one generation of selection, g decreased by 23%:

Slide 1 cropped

So how do we find the generation at which allele g is less than 1%?

Before we jump to those calculations, let’s consider what these numbers really mean.  After the first round of selection, the frequency of g is 23.1% or 0.231.  This number includes the individuals who are gg, even though they are sterile.  Why is that?  Because when Gg heterozygotes mate, their children will be:

1 GG: 2 Gg: 1 gg

The fact that Gg individuals have normal fertility means that there will be gg children, even though those children are not able to reproduce.

Also, let’s consider the number of Gg heterozygotes in the population after one round of selection pressure.  Again, the frequency of g is 0.231.  The number of Gg hets = 2pq.

2pq = 2(0.769)(0.231) = 0.355 or 35.5%

35% of the population here is Gg, which means that g is being propagated by about a third of the population (a substantial fraction!).

Let’s move on to the calculations to determine when the frequency of g will be less than 1%.

I doubt that you’d be asked to solve a problem like this on an exam without being able to use Excel or a similar program.  The calculations are easy on a spreadsheet but very tedious to do by hand.  I used Excel to solve this problem.  Here’s what my spreadsheet looked like to set up the calculations:

Slide 2

Here are the entries I put into Excel to set up this spreadsheet: 

Cell B1: 0.3 (original value of g before selection)

Cell B6: =B1/(1+B1)

(this is the calculation for g after each round of selection: g’ = g/(1+g))

Cell B7: =B6/(1+B6)

Cells B8-B14: Copy/Paste from cell B7 down to B14.

From the image above, you can see that after 9 rounds of selection (Row 14), the frequency of g is 0.081 or 8.1%.  So we’re not done, and we can continue our calculations by copy/pasting Cells A14 and B14 until we reach…

Slide 3

…Cell 102!

We’re looking for the generation at which q drops below 0.01, which happens to occur at the 97th generation of selective pressure.  What’s so interesting to me as a geneticist is that g (or q, in Hardy-Weinberg terms) can persist for so long when gg individuals are sterile.  This example illustrates why recessive deleterious alleles are not easily eliminated from the population.  As long as Gg heterozygotes are healthy, then g will be in the allele pool for a long time.

So that was a lesson on selective pressure and Microsoft Excel techniques.  Got questions, comments, or something else to say?  Tell me in the comments below! 

Thanks for reading!

A Little Something Inspirational

As your new semester gets underway, remember that…

“Education is not filling a bucket, but lighting a fire.” ~William Yates

Happy learning to you!

Tuesday, September 2, 2014

A Personal Post

Found Heart

Today, as I write this post, my dad is in an operating room, where his team is working to save his life.

Dad is a rather private person (unlike me, who has three blogs and writes about her personal life on a regular basis), so I’m not going to share any details about his illness.  Instead, I want to talk about cynicism, service, and the meaning of one person’s life.

I’ve been working in the biomedical sciences for eleven years now—six years in grad school, another four-ish doing research, and less than a year of tutoring biology and chemistry students.  I often feel a sense of cynicism from my colleagues about premedical students and their behavior, which is ultimately motivated by a fear of not being good enough: the obsession with getting the best grades and the best test scores.  We lose track of the awesome, humbling goal of medicine: to save lives.  My dad’s surgical team, if they are successful, will save his life today.  How incredible is that?!

My dad has been receiving the best that modern medicine has to offer.  He is one person, and his life is worth the best.

As a tutor, I sometimes struggle with the feeling that my work doesn’t matter, that helping one person at a time isn’t really helping anybody.  It’s a cynical view, the same cynical view that sees premedical students as more concerned with their grades than with helping other people.  It’s an ego-driven view, one that says I’m too important to spend my time helping one student at a time.  I should be doing something BIGGER.

My dad: one person.  Each student: one person.  All of them, one person at a time, deserving of the best care that we can offer them, in our own ways.

Ultimately, some of my students will go on to be doctors, nurses, and other medical professionals.  They too will save lives, and how amazing is that?!  When I think about those career paths, I can see that we exist in a circle of service: we who teach help our students become health professionals, and they go on to take care of all of us, one life at a time.

“On my deathbed I will be grateful for each choice of connection, love, and service,” writes Charles Eisenstein in The More Beautiful World Our Hearts Know is Possible.  I think those of us who choose teaching or medicine intuitively know the truth in Eisenstein’s words.  We make the world a better place, helping one person at at a time.  If that’s the scale on which our work unfolds, then let us embrace that.  Let’s celebrate it!  We aren’t small just because our work happens on a small scale.  We are big because our work sends out ripples of love into the wider world.  Today, a group of medical professionals put all of their expertise together to save one life, my dad.  This semester, I will give each of my students the best I can offer, whether here on this website or sitting down together in a coffee shop, solving chemistry problems together.  Each act of service is an attempt at excellence, at meeting a real need coming from a real person.

How amazing is that!

Monday, September 1, 2014

LESSON: Selection Pressure and Changing Allele Frequencies

We’ve used Hardy-Weinberg equilibria to determine phenotype frequencies in a population.  The Hardy-Weinberg equations assume that a population is stable.  In other words, allele frequencies are not changing—there’s no selection pressure.

But what happens when selection is acting upon a population?  Theoretically, we understand that selection will favor certain alleles or allele combinations over others.  This will shift the balance of alleles toward a new equilibrium.  If we know the magnitude of the selection pressure, we can calculate the effect of selection on allele frequencies.

Let’s work through a sample problem to unpack this set of questions. 

You and your medical team are summoned to Capitol City, where a strange epidemic has rendered 9% of the population sterile. Working rapidly, you discover that there’s a strong correlation between Factor G, a protein found in blood, and the fertile residents: all the fertile residents test positive for Factor G, but all the infertile residents test negative for Factor G. Later genetic and biochemical tests reveal that the population of Capitol City carries two alleles for a gene that is necessary for the production of Factor G such that G is dominant to g. All the fertile residents are genotypically GG or Gg. All gg individuals are now sterile. The original frequencies of G and g were as follows:

G = 0.7

g = 0.3

After the epidemic, what are the allele frequencies of G and g in the next generation?

Let’s define a new term first.

* Fitness, W.  Fitness is a measure of reproductive success and should be a value between 0 and 1.  If there is no selection pressure reducing the reproductive success of a genotype, then W = 1.  If a genotype cannot reproduce (as in our sample problem above, where gg individuals are sterile), then W = 0.

So for our sample problem:

For GG, W = 1

For Gg, W = 1

For gg, W = 0.

We’ll make use of these values below. 

Now we need to dive deeper into the math to connect s to Hardy-Weinberg equilibria.

Slide1 cropped

Slide2

We could have predicted that if q2 = 0, then p2 + 2pq = 1.  So that set of calculations confirms our prediction, but we still have no idea what p and q are after selection.  We need another set of equations for that task.

Slide3

Slide4 cropped

Slide5 cropped

Slide6

Slide 7 redo cropped

Slide 8 cropped

And there you have it!  Now it’s your turn: what if the epidemic, rather than making gg individuals sterile, reduced their fertility by 50%  What would the frequency of G and g be after one round of selection pressure?  (I’ll provide or confirm the answer in the comments when someone asks for it.) 

References:

Comprehensive Genetics coursepack, 2014 version, published by Dr. John Ellison, Texas A&M University

TAMU Genetics 301 Tutoring for Fall 2014

Happy first day of classes, TAMU students!

I’ll be offering on-line tutoring this semester for Genetics 301, as taught by Dr. John Ellison.  I have tutored several students in this class, and my students have been really happy with their sessions.  I love this challenging class, and I love helping students better understand the material.  I recently acquired the book containing class Powerpoint slides and practice exams, so that will facilitate easier tutoring sessions for my next batch of students.

I’m located in Austin, TX, having recently moved from College Station.  My Genetics 301 sessions will be on-line.  As a recent student commented, being able to do tutoring sessions at home in your pajamas is awesome!  My partner, Tutor Paul, has set up on-line tutoring for both of us.  (Some of you might know Tutor Paul; he’s the guy you want to see for tutoring in mechanical engineering, math, or physics.  He’s awesome.)

So what do you need for on-line tutoring?

* A high-speed internet connection, a computer, and a microphone.  If you want me to be able to see you, you’ll need a webcam as well.

* A Google+ account

* The plug-in for Google+ Hang-outs

During an on-line tutoring session, you’ll be able to see my face, hear my voice, and see my whiteboard in which I work out problems and illustrate concepts.  Paul and I are dedicated to creating an awesome on-line tutoring experience for our students, so we invite you to try it out with us.  Contact me for more information!  Call or text 847-644-0782.  (You can also e-mail me at r-meissner@u.northwestern.edu)

Happy learning and have a great semester!

Saturday, August 30, 2014

What Happens During My Tutoring Sessions?

August 26 2014 iPhone 025

I’ve been in a few situations in the past week which have got me thinking that people have preconceived (and inaccurate!) ideas of what happens during a tutoring session.  I want to offer some insights into what I do as a tutor.

My sessions are, as a rule, student-led.  As a tutor, I am here to meet my students’ needs, and I want their needs to guide our sessions.  That means I’m not following a script or a checklist.  I’m listening to my students, hearing their concerns, their confusions.  I’m finding them on the map of learning and meeting them there.

A tutoring strength of mine is flexibility.  Because I don’t have preconceived notions of what any given tutoring session should look or feel like, I feel very free to make each session unique.  That’s not to say that I feel compelled to reinvent the wheel, but I think there is enormous power in the collaboration between tutor and student.

Allow me to be give you some concrete examples of what can happen in my tutoring sessions.

* We can start from “I’m totally lost in this class.”  It’s not uncommon for students to tell me they are lost and frustrated with a class.  I have such love and admiration for their willingness to tell me how they are feeling.  That takes courage.  When a student is lost, we start a dialogue so I can find a starting point for our lessons.  From there, I can create entire customized lessons to help my student build a base of knowledge.  Generally, I think that simple is better in these situations.  Yes, science is large and complex, and I don’t mean to diminish that truth.  But we learn new ideas in bite-sized chunks, and I think it’s better for my student to walk away from a tutoring session with one new idea that they understand rather than five ideas that leave them confused and frustrated.

* Lessons can be improvised from homework, practice problems, or class notes.  Much of what I do is teaching mini-lessons that are centered around exam preparation.  Feedback from students on these tutoring sessions has been really positive, so I’m happy to keep going.  My students crave more than the right answers.  They genuinely want to understand the how and why of their subjects.  I strive to create interactive sessions so that my students are actively engaged as we work through the material.  Many students want to participate, and I’m happy to co-create our learning environment with them.

* Yes, sometimes we work through homework assignments together.  We do homework together.  Homework is the bread and butter of learning.  Again, my students are seeking an understanding, not just the right answers.  When we work through the homework, we’re having a conversation.  And if a mini-lesson is needed, then that’s what we do together.

* I share resources, advice, and exam strategies.  I’m aware that many students feel the pressure to get it all done, so time is of the essence.  My partner, Tutor Paul, has said that his students work with him because he’s able to save them so much study time in their upper-level engineering classes.

Paul and I function as learning resources to help students with their academic goals.  As such, we share the knowledge and wisdom we’ve accumulated over many years of being students ourselves and the years we’ve spent tutoring.  We are here to help!

I may write a post in the future about some of the resources and advice we offer.  That’s such a big topic that it deserves its own post.

And now it’s your turn: have you ever worked with a tutor?  What was your experience like?  Would you work with a tutor again?

(And if you have any questions for me about my tutoring, feel free to ask them below in the comments!  Happy learning.)

Monday, August 25, 2014

LESSON: Heat Transfer, Part Two

If you’re new to this site, here is Part One of my lesson on heat transfer.  This lesson will be building on the ideas from Part One.

Now we’ve established that we can calculate values for heat transfer using the formula q = nC[DeltaT].  (Pretend that Delta is a triangle, please.)  Let’s work through a more difficult problem.  This one comes from Chemistry (Third Edition) by John Olsmsted III and Gregory M. Williams.

A silver coin weighing 27.4 g is heated to 100.0 degrees C in boiling water.  It is then dropped into 37.5 g of water initially at 20.5 degrees C.  Find the final temperature of water and coin.

Slide1 cropped

Here is an example of a problem in which we cannot just look at the values given by the problem and perform a plug-and-play calculation.  We are going to use q = nC[DeltaT] but not before we do some algebra work.  Let’s consider the values we have on hand.

Slide1

Slide2

Do you see the dilemma?  We have two unknowns, which means we can’t simply plug and play to get an answer.

But notice that we have the same unknowns for the silver coin and water, so perhaps we can use the set of unknowns to set up an algebra equation with a single unknown.

In this problem, we start off with two different systems: the hot silver coin and the room temperature water.  When the coin is dropped into the water, it will transfer heat to the water until the new “system” (coin + water) are at equilibrium, which means SAME TEMPERATURE.  (Also, does “transfer heat” mean anything to you?  If you guessed q, as in heat flow, then you are correct and you get a gold star. )

To put this in mathematical terms:

-qcoin = +qwater   

All the heat that flows out of the coin will be heat that flows into the water.  Furthermore, if q = nC[deltaT], then:

-(nC[deltaT])coin = (nC[deltaT])water   

And now we’ve reduced our unknown to one term, final temperature Tf.

Here is the full-length solution, starting from the equation above.

Slide Four cropped

And there you have it!  Now it’s your turn: using the same problem from above, what would the final temperature of water and coin be if the coin were made of pure copper?  The molar heat capacity of copper is 24.435 J/mol K.

(I’ll provide the answer if someone asks for it in the comments.)

Saturday, August 23, 2014

More Drawing, More Learning

If you feel like you are living inside the pressure cooker of perfection, let me assure you :

You are not alone.

I have a hypothesis that collectively, we have become so good at the game of school and scholarly achievement that what used to be learning has been replaced by an unrelenting pressure to get straight A’s and achieve, achieve, achieve at all costs.  A sad price for this pressure is a loss of creativity and innovation.  But learning doesn’t happen without risk.  How can I encourage you to take some risks in your academic life?

I’ll start by offering a confession: I wish I were perfect, but I know I’m not.  To accept my less-than-perfect nature is a daily challenge.  For me, grace is found in the space where I can accept myself as I really am.  Grace is also found in that space where I am striving for something I want.  This is the paradox of ambition: it gives us a goal, something for which to strive, yet we don’t want to pin our self-worth on the achievement of that goal.  It’s okay to fail, and it’s okay to not want to fail.

This month, I’ve been reviewing thermodynamics at the general chemistry level, and I decided to make a “mind map” for myself.  A mind map is a a brainstorming diagram in which you connect ideas, write notes for yourself, even draw images if that’s your thing.  I had the idea that I would share my mind map on this site, but as I drew it, I started to think to myself, Oh, it’s not good enough to share.  It’s messy.  Other people will think it’s not pretty enough.

And then I realized the mind map had something to teach me, which is that learning is messy.  If I want my students to feel comfortable making mistakes, then maybe I should give myself the same grace.  Plus, mind maps are awesome!  They're great for studying.  To make a mind map, you have to actively engage with the material, which I find is better for studying and remembering the important ideas.

So here is my messy mind map for thermodynamics.  Feel free to use it for your own studying!  Or draw your own mind map to help you learn a new subject.  If you prefer to download it, I’ve included a link below for that too. 

Thermodynamics Mind Map_small RM{Rose-Anne’s Thermodynamics Mind Map. Click on the image to see a bigger version!}

Click to download the Thermodynamics Mind Map from Google Drive

Friday, August 22, 2014

Chemistry Lessons

This page is an index of all the general chemistry lessons I’ve published on this site. Enjoy and happy learning!

(Have any questions for me? Connect with me by e-mail at r-meissner@u.northwestern.edu or on Twitter. I’m @wormthoughts.)

* Heat Transfer: Part One

* Heat Transfer: Part Two 

* And to help you study: some study tips to do your best in general chemistry

Genetics Lessons

This page is an index of all the genetics lessons I’ve published on this site.  Enjoy and happy learning!

(Have any questions for me?  Connect with me by e-mail at r-meissner@u.northwestern.edu or on Twitter.  I’m @wormthoughts.)

* Conditional Probability (written with Tutor Paul)

* Mitotic Recombination: Twin Spots

* Human Blood Type and Population Genetics

* Selection Pressure and Changing Allele Frequencies

* Selection Pressure, Part Two

Bonus: here are some great on-line resources for genetics.

* How radiation can damage DNA (the first graphic on this page is terrific)

* A good (and very technical) guide to types of DNA damage

Thursday, August 21, 2014

LESSON: Heat Transfer, Part One

I wrote recently about the importance of algebra in general chemistry.  To illustrate, I’m going to present a lesson in two parts.  This first part is an example of what I call “plug and play” chemistry problems.

I’ve been brushing up on thermodynamics at the gen chem level.  Thermodynamics is a very math-driven branch of chemistry, so it’s a lot of equations and a little bit of theory.  There are at least two conceptual ways to approach problems:

1) Envision the process being described, determine the unknowns, then select the appropriate equation that describes (mathematically) the flow of energy in the system.

2)  Write down the values provides (such as heat capacity and initial temperature) and the value for which you have to solve (such as final temperature), find a formula that contains those terms, then solve for the unknown.

Option #1 is definitely the better choice and the one for which we should strive as we’re learning.  But if I’m honest, I think a lot of us are tempted to use #2 if we can get away with it.  In the second part of this lesson, I’ll show you an example of how option #2 can be insufficient.  Additionally, thermodynamics uses signs (+/-) to indicate the flow of energy into or out of a system.  Because of that, it’s a really good idea to get in the habit of imagining the process so you can double check your math and your signs.  (Or draw it out!  Drawing is always a good idea when studying science.)

(More on drawing later, I think.  It’s a topic worth exploring for science students.)

Let’s consider the following problem and how to find a solution.

You drop a pure copper penny on the ground while walking to breakfast one day.  The penny’s mass is 2.50 g.  At the time you lost it, the penny’s temperature was 20 degrees C.  When you find it later, the penny is 25 degrees C.  How much energy did the penny absorb from its surroundings between the time you lost it and the time you recovered it?

This problem is pretty simple, but let’s draw a diagram so we can visualize the energy flow.

Slide1 cropped

Heat is flowing into the copper penny from the sun, thus raising the temperature of the copper.

Now let’s apply some technical labels to help us find the right formula.

Slide2 cropped

A quick review of terms:

q = heat flow, usually measured in Joules (J).

Ti = initial temperature (can be degrees C or K)

Tf = final temperature (must have the same units as Ti)

What else do we need to know to solve this problem?  We need to know how easily copper absorbs heat from its surroundings.  This material property is known as heat capacity, and the heat capacity is different for different substances.  The molar heat capacity for copper at 25 degrees C is 24.435 J/mol K.  What does this value mean?  It means that 1 mole of copper requires 24.435 J to raise the temperature 1 K.

(For our purposes, we’ll assume that the heat capacity for copper is the same at 20 degrees C and 25 degrees C.)

Which formula expresses the thermodynamic question asked in this question?

Slide3 cropped

Now that we have a formula to connect heat flow to the change in temperature in a specific substance, we can plug in the values from above and solve the problem.

Slide4 edited

(Note that in this problem, K and C are interchangeable because a 5 degree difference in Kelvins is the same as a 5 degree difference in degrees C.)

So that’s thermodynamics, plug-and-play style.  Once you have an answer, it’s good to consider whether your answer is reasonable in units and magnitude.  In this problem, we have a small object that has increased in temperature by a modest number of degrees.  4.81 J is a small amount of energy, so this answer seems reasonable to me. 

Next up: a similar problem that will require more conceptual heavy lifting on our part.

Now it’s your turn:

You decide to cook some pancakes in a cast-iron skillet on your electric stove.  You apply 2000 J of heat to your very heavy (3.31 kg) skillet, which was initially at room temperature (22 degrees C).  If 375 degrees F is the ideal temperature for cooking pancakes, do you need to apply more or less heat to achieve that temperature?  Assume the skillet is pure iron for this problem.

* * *

Bonus fun facts:

Pennies were made of pure copper from 1793 to 1837.  {Source}

375 degrees F as a temperature for cooking pancakes?  Who knows—I always cook pancakes by feel.  But here’s a discussion about griddle temp for pancakes.

Wednesday, August 20, 2014

LESSON: Human Blood Type and Population Genetics

Today’s lesson is inspired by one of the questions a student asked me earlier this summer.  We’ll be discussing human blood types and population genetics, including how to solve problems on this topic.

The question:

In Capitol City, the allele frequencies of human ABO blood types are as follows:

IA = 0.2

IB = 0.3

IO = 0.5

What is the frequency of type A blood within Capitol City’s population?

There is a lot to know and unpack from this problem.  Let’s start with a quick review of blood types.

Recall that for blood types, A and B refer to the presence of the A and B antigens, respectively, present on red blood cells.  Type A red blood cells express the A antigen; Type B red blood cells express the B antigen.  Type O blood expresses neither A nor B antigen.  That means two genotypes can code for blood that is phenotypically type A:

IA IA or IA IO

(Why two genotypes?  Because the IO allele does not code for an antigen.  Instead, the IO allele contains a mutation that results in a protein that lacks enzymatic activity.)

Similarly, two genotypes can code for blood that is phenotypically type B:

IB IB or IB IO

Finally, only one genotype can code for blood that is phenotypically type O:

IO IO

Now that we’ve established our genotype/phenotype relationships, let’s shift our attention to the second aspect of this question: population genetics.

When you see the words “population genetics,” you should immediately think of this phrase: Hardy-Weinberg equilibrium.  The simplest version of Hardy-Weinberg equilibrium is a population that contains two alleles for a gene.  Let’s say these alleles are A and a, where A is completely dominant to a.  In Hardy-Weinberg terms, A and a are equivalent to p and q, the two alleles in our system.  The Hardy-Weinberg equations (shown below) allow us to move between allele frequencies and genotype frequencies.  We use algebra to do these calculations.

Slide1

Slide2

To apply Hardy-Weinberg to our two-allele system, A and a, we would have the following:

pp = AA

pq = Aa

qq = aa  

Let’s apply some numbers here to see how the math works out for a two-allele system.  Let’s say that a population has the following frequencies for the A and a alleles:

A = 0.2

a = 0.8

(Note that it’s entirely possible for a recessive allele to be the most common allele in a population.  Genetic dominance does not imply that it’s the most frequently found allele.)

To calculate the frequency of the three possible genotypes (AA, Aa, and aa), we use the binomial expansion from Hardy-Weinberg:

AA = pp = (0.2)(0.2) = 0.04

Aa = 2pq = 2(0.2)(0.8) = 0.32

aa = qq = (0.8)(0.8) = 0.64

Note that our genotype frequencies should add up to 1, which they do!  Success!

Now, let’s turn our attention back to ABO blood types.  We can’t use our two-allele Hardy-Weinberg equation here because we have three alleles.  Instead, we can modify the equations to include a third allele:

Slide 3 REDO 8_06 PM

By squaring the trinomial, we now have equations we can use to calculate the frequency of particular genotypes or phenotypes if we have the allele frequencies.

Now let’s solve the original problem in four steps.

Slide4 cropped

Slide5 cropped

Slide6

Slide7

Alright, now it’s your turn!  Using the data above for Capitol City, what is the frequency of Type AB blood in that population?

* * *

More resources:

* ABO blood types via Wikipedia (a bit dense but still useful for more information)

Sunday, August 10, 2014

LESSON: Mitotic Recombination: Twin Spots

This post will be my first lesson on this site.  I offer these lessons as a gift in the spirit of Sacred Economics by Charles Eisenstein.  If you’ve arrived at this post, I assume you are looking for some help to better understand the classic phenotypes that are seen in studies of mitotic recombination.  In this lesson, I’ll explain the mechanism that may explain one phenotype, twin spots.  Here is a very simple graphic to illustrate the twin spots phenotype:

Figure 1_twin spots graphic

We can see that we have two “spots” on the fly’s back (dorsal surface for you anatomy fans), right next to each other, and each spot shows a different mutant phenotype (which I’ll explain below).  Note that the wild-type phenotype is a brownish-beige body and straight-ish bristles.

Mitotic recombination is the phenomenon whereby homologous chromosomes swap portions of DNA with each other in non-meiotic cells.  It’s a rare event and often induced either by X-ray radiation or by transgenes that cut and splice DNA when they are expressed.  One of the most interesting questions that can be answered by mitotic recombination is whether a phenotype is cell autonomous.  In other words, is the phenotype of a cell or patch of cells due to the genetic activity within that cell or patch of cells, or does it depend on the genetic activity of a different cell?

In Drosophila, we can study mitotic recombination using mutant alleles that affect the appearance of the body surface.  Dr. Curt Stern did just this using alleles for two genes: yellow (y) and singed (sn)1.  Homozygous yellow mutants have a yellow body color, while homozygous singed mutants have bent, funky-looking bristles.

(Check it out: yellow mutants and singed mutants.  For the singed mutants, compare D [a wild-type control called Oregon R] to A [a singed mutant].)

Stern worked with female flies that were heterozygous for yellow and singed.  These genes are on homologous chromosomes.  In Stern’s experiment, the mutations were on different but homologous chromosomes.  We can write this genotype like this:

Figure 2_Genotype notation

y+ sn- is the genotype of one chromosome, and y- sn+ is the genotype of the other.  Heterozygous mutants like this are also called trans-heterozygotes because the mutations are found on different chromosomes.

Most of the animals Stern examined were wild-type in appearance.  In other words, their body color and bristles did not show mutant phenotypes.  This is what we would expect in animals that have a wild-type copy of each gene.  But sometimes he observed what were dubbed “twin spots” where a spot of yellow was adjacent to a spot of singed bristles.  This cartoon is a nice illustration of the phenotype.  Because of the location of these twin spots, Stern proposed that they were the product of mitotic recombination between the centromere and two loci located on the same side of a chromosome.

So how would that mechanism work?  Let’s draw it out and follow the chromosomes through cell division.

First, let’s consider what the chromosomes look like without mitotic recombination.  For simplicity, I have omitted everything but the most essential details in the diagrams below.  CENT is the centromere of the each chromosome.

Figure 3_Parent cell

Now let’s look at what happens when this parent cell divides in the absence of mitotic recombination.  Here I show the cell before and after it synthesizes new DNA, which results in the replication of the chromosomes.  Note that formally, DNA synthesis is not part of mitosis.  Instead, it is considered part of the cell cycle.

Slide4

Now that we’ve replicated our homologous chromosomes, let’s follow them through mitosis and cytokinesis.  Note that after the chromosomes have replicated, the sister chromatids are connected via the centromere (CENT in the figure).  This organization will allow sister chromatids to be separated during mitosis and pulled apart into the nuclei of the two daughter cells.  The dotted line below represents cytokinesis, or the dividing of the parent cell’s cytoplasm into two daughter cells.

Slide5

Note that after this cell divides, the daughter cells would have the same genotype (sn- y+/sn+ y-).  Note that all of these cells would show a wild-type phenotype because each cell has a wild-type copy of sn and y.

Now, let’s consider a situation where mitotic recombination occurs.  Scientists aren’t really sure when mitotic recombination happens.  Some think it happens during interphase; that’s what I have shown below (specifically, Gap 2 after DNA synthesis is completed).  The take-home point: mitotic recombination will switch the order of specific sn and y alleles compared to the original parent cell.

First I’ll show the recombination step and the reordered chromosomes.  Note that recombination is taking place between chromosomes 2 and 3.  Also note that the recombination breakpoint is between the centromere and the singed locus.

Slide6 

Now we have paired chromatids that have different genotypes.  Chromatids 1 and 2 no longer match, but as you’ll see below, they will segregate during mitosis as though they are genetically identical.  The same thing is true for chromatids 3 and 4.

Let’s follow the chromosomes through mitosis. 

Slide7

Because of the recombination event that happened during Gap 2, we end up with daughter cells that have different genotypes.  Instead of the sn- y+/sn+ y- genotype that the parent cell has, our daughter cells are as follows:

Genotype_Phenotype Chart

And finally, here is a cartoon to show how mitotic recombination in a precursor or parent cell could give rise to a twin spot.  The idea here is after the parent cell undergoes mitotic recombination, the new daughter cells replicate themselves and make small populations that we can see visibly as the yellow or singed spots.  (Pardon the reverse orientation on the spots; here I’ve shown the yellow spot on top and the singed spot on the bottom.)

Slide8

References:

1Stern, C (1935) The effect of yellow-scute gene deficiency on somatic cells of Drosophila. Proc Natl Acad Sci USA 21: 374-379.  {Find the full-length paper here.

For more learning, I like the following links:

* Mosaic Analysis [in Drosophila]

* A good review of what happens to chromosomes during the cell cycle and mitosis 

* * *

Like what you just read?  To connect with me, you can find me on Twitter (I’m @wormthoughts) or by e-mail (r-meissner@u.northwestern.edu).  Or leave a comment below!

Thanks for stopping by!

Tuesday, August 5, 2014

The Purpose of This Site

The purpose of this website is threefold:

1)  I want to make my lessons, resources, and knowledge freely available to students.  This site provides a space where I can present and share lessons for students who may be seeking additional learning resources for their studying.

2)  I want to market my services to current and potential students.  While the contents of the site are offered as a gift, my tutoring is a paid service.  If you’d like to work with me as a tutor in person or on-line, I’d love to work with you!  Information about my rates and educational credentials can be found here.  You may contact me by e-mail (r-meissner@u.northwestern.edu) or phone/text (847-644-0782).  I am generally available for tutoring from 11 AM to 8 PM.

3)  I make general announcements on this site, so check back frequently for updates!

Thanks for visiting me!  Happy learning.  

Monday, August 4, 2014

STUDY TIPS: General Chemistry

I’ve had the pleasure of working with several students in general chemistry this year.  It’s interesting to see chemistry through the eyes of my students.  General chemistry came easily to me as a student; as a tutor, I find myself asking, “When it comes to learning this material, what works?  What doesn’t?  What holes can we fill so that my students have an easier time with the exam?”

Here’s my list of study tips for general chemistry.  What you won’t find here: very basic tips like go to class, pay attention, take notes, work the problem sets.  I assume you know these things.  (But I’ll come back to that point about working the problem sets!)

* You must master the theory and application of chemistry concepts.  What do I mean by this?  Chemistry is a marriage of theoretical ideas, such as equilibrium, and the application of those ideas, such as calculating the equilibrium constant Keq value if I tell you the concentration of products and reactants in a solution at equilibrium.  A theory question might ask you to predict the direction of a reaction if the reaction quotient Q is less than Keq.  (Answer: the reaction will keep generating products until Q = Keq.)  (Pop quiz question: what’s the difference between Q and Keq?)

Many gen chem exams will mix together theoretical questions and math-based application questions.  You’ll want to be able to answer both.

“What if I don’t have practice questions for theoretical concepts?”  If you are lacking study materials, get in touch with me.  I’ve got a library of chemistry textbooks and practice exams to help you work on mastering gen chem theory.

* You must learn to think in four dimensions: the X, Y, and Z planes and time.  Chemistry takes place across all four of these dimensions.  Students who are, shall we say, spatially challenged (like myself) are going to have to focus their efforts on mastering three-dimensional chemistry.

A simple example from gen chem is molecular geometry: where do electron pairs (lone pairs or the shared pairs of a chemical bond) localize around an atom’s nucleus?  In other words, what is the three-dimensional shape that defines where the electrons are in space?  (Answer: it depends on how many of them we have around an atom.)

The question about time looms large when we start to talk about reaction kinetics.  This topic may be discussed in an abstract way, such as in spontaneous reactions that happen so slowly that they appear to be not spontaneous (such as combustion reactions that require energy, such as a spark, in order to begin), or we might talk specifically about reaction rates and rate constants.

* Work those practice problems, especially the practice exams.  Then practice some more.  It’s not enough to review your notes and think you understand the material.  Practice problems demand that you understand the material and are able to apply it to solve problems.

If I could offer one piece of advice to gen chem students, it would be to focus your study time on practice exams (assuming your instructor provides them to you).  Work as many of the problems as you can.  If you struggle through any problems, go back and work them again.  Try to see the logic that is applied to each problem so that when a similar problem shows up on your real exam, you know how to analyze it.

* Seek out additional learning materials.  I’m going to be really honest here: I dislike a lot of textbooks.  I hated my gen chem textbook in college.  If you find yourself in a similar position, don’t hesitate to seek out additional learning materials.  I’ve been using an awesome chemistry textbook in my tutoring that I can recommend: Chemistry (Third Edition) by Olmsted & Williams.

Also, this is the age of the internet!  There are so many wonderful on-line study materials (including this blog!).  I particularly like ChemWiki and MIT OpenCourseWare on youtube.  (As an aside, as much as I love Wikipedia, I don’t like it as much for studying chemistry.  And that’s okay.  The important thing is to find resources that work for you.)

* Make sure your algebra skills are strong.  A lot of problem-solving in gen chem comes down to setting up the problem as an algebra equation to be solved.  If you feel your algebra skills are weak, you might want to spend some time working on them either before you start gen chem or while you are in the class.  The more you can solve for X, the more comfortable you’ll be with chemistry problems.

* Learn to think about chemistry in terms of units. This tip comes from my partner, Tutor Paul, who has been tutoring engineering students for years.  When solving equations, we want units within a problem to match and cancel out.

One way to test your comfort with units is to do a little free word association.  What unit words come to mind when I say the following?

- energy?

- stoichiometry?

- pressure?

- volume?

- concentration?

For me, I have the following associations:

- energy? Joules.

- stoichiometry? Moles.  Or molar ratios.

- pressure? Atmospheres.

- volume? Liters.

- concentration? Moles per Liter.

My answers are standard units in which amounts are expressed.  A Joule is a unit of energy.  The stoichiometry of a reaction is expressed in moles (or molar ratios).  And so on.  Getting comfortable with gen chem means getting comfortable with units.

* * *

Readers, what else would you add to this list?  Tell me in the comments!

Happy studying!