Linked Genes

We started class with a warm up asking you to write down everything you know about how we get our eye color.  If you want to learn more about some interesting genetics questions you can link to http://www.thetech.org/genetics/asklist.php. 

Next we discussed the reading, 15.1 and 15.2.  Most students did not have any questions from 15.1, but 15.2 was a struggle.  I went through an example on the board, first showing what would happen during meiosis if two genes were not on the same chromosome (not linked) and then repeated the exercise for when they are on the same chromosome (linked).  This resulted in two different expected outcomes of a cross.  I used this example to introduce crossover and explain how crossover during meiosis results in new combinations of alleles on a chromosome. 

Finally we went over how to determine the relative locations of genes on a chromosome based on their crossover rate. 

For homework I asked students to make sure they understood problems 1-5 (ignore #6) from the homework linked on the last post.

On Monday I will address any questions on the homework before we complete a lab activity (don't get too excited, it is based on pictures of fungal spores :))

Block Day - Eye Color Genetics

Was it hard to stay on task today or was it just me?

In class we mainly focused on finishing up the case of Alexia and Evan who are both blue-eyed, but have a brown-eyed child named Ryan.  The case revealed the multiple genes involved directly in eye color and suggested several others that could influence the final color seen.

While students were working on the case there were several side conversations that ventured into the areas of chimerism (and search for "I Am My Own Twin" which originally aired on the Discovery Channel), dermoid cysts, conjoined twins, and more.

For homework tonight I am asking you to read 15.1 and 15.2.  Then go to this LINK https://docs.google.com/document/d/1lIcrXCROg2eC5c8AURkO-Zp5EGifMbkJanF8ZTvMm5s/edit?hl=en&authkey=COKx_q0B and answer the 6 questions on the Chapter 15.2 Worksheet.

I am also linking you to a few excellent sources below:
BioCoach at http://www.phschool.com/science/biology_place/biocoach/inheritance/intro.html
Your textbook web site.  Go to Chapter 15 and go through Activity 15.2.
Lab Bench Activity reviewing Meiosis, Crossover and how this relates to Linked Genes.

Complexity of heredity

Today in class I did a reading check by asking students to define and give examples of:
complete dominance, codominance, incomplete dominance, pleitropy, epistasis, polygenic inheritance.
We then had a discussion of the last three terms using the examples of Marfan Syndrome and cystic fibrosis for pleiotropy, albinism for epistasis, and height and skin color for polygenics.

We ended by looking at the pedigree for hemophilia and having a quick discussion of its impact on history.

No homework tonight.  Enjoy it.