Announcements

1. Announcements Put Homework 2 on table at front of classroom

2. BIO 304 Lecture 6

3. Lethal alleles

4. Combinations of 2 gene pairs, 2 modes of inheritance A woman of blood type AB marries who is a carrier of the recessive cystic fibrosis disease gene marries a man of blood type O who is also a CF carrier. 1. What is the probability that their first child will be a daughter of blood type A who is unaffected with CF? 2. What is the probability that their first child will be a son of blood type AB who has CF?

5. What is your familiarity with the concept of genetic epistasis; have you worked many word problems that deal with epistasis? 1. I'm all over it. I could do these problems in my sleep. 2. I've covered it in classes before and have worked some problems through. 3. I've heard of epistasis before, but have never worked any problems. 4. The concept is completely new for me.

6. Epistasis Developmental pathway Signal transduction pathway Biosynthetic pathway

7. Types of epistasis gene A gene B enzyme A enzyme B colorless red purple

8. gene A gene B enzyme A enzyme B colorless red purple

9. gene A gene B enzyme A enzyme B colorless colorless purple

10. light blue A colorless dark blue B light blue

11. A colorless blue green B colorless yellow

12. In humans, albinism is an autosomal recessive condition. Two albinos marry, and they have four normally pigmented children. What is the most likely explanation for this result? 1. Albinism is lethal, so only the normally pigmented embryos survive to term. 2. A mutation occurred in one of the parent's gametes, causing a reversion of the albino allele back to wild type. ✓ 3. Two different genes can cause albinism. Each parent was homozygous mutant for one of the genes but not the other. 4. That outcome is not genetically possible -- the children must have been adopted.

13. Answer to clicker question: normal pigmentation