Lecture07S10 - BIS101/Engebrecht Lecture07 Announcements...

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BIS101/Engebrecht Lecture07 4/13/10 Announcements: Key for Homework01 is posted under resources. I have also posted a practice midterm under “Resources” “Test Information”. Midterm I is Thursday April 22. You did very well on the quiz – I went over problem 9 as the most people got that incorrect. On Friday we discussed gene interactions. There are four gene interactions I would like you to know: Complementary gene action (9:7); Recessive Epistatsis (9:3:4); Recessive suppression (13:3) and Duplicate genes (15:1). I also told you that it will help you if you recognize the altered ratios in the F2. CQ1: With respect to the hypothetical biochemical pathway, either A or C is correct and you cannot distinguish; therefore, the answer is D. CQ2: Since this is complementary gene action, you would predict a 9:7 ratio in the F2 of blue to colorless ( Answer C ). CQ3: The 13:3 ratio in the F2 suggests that it is recessive suppression ( Answer C ). CQ4: With respect to the genotype of the parents, it has to be PPss x ppSS ( Answer B ), if it was PPSS x ppss then both parents would be purple. Summary The present extensions to Mendelian genetics concern gene action. Gene action and inheritance are independent. However, gene actions influence the phenotypes, which will influence the expected phenotypic classes in the F2. This analysis enables geneticist to elucidate the function of genes in pathways. While you can work out the consequences of such gene interactions, recognizing the alteration in ratios will greatly facilitate determining how genes are interacting. Gene linkage We began our discussion of genetic linkage. Most of you understood when we began our discussion of genes on the first day of class that genes reside on chromosomes in a fixed location. It thus follows that genes can display genetic linkage. Genetic linkage is defined as 2 genes being in close proximity to each other. This will result in a distortion in the ratio of progeny obtained when examining linked genes in genetic crosses. Genetic linkage was first discovered by Morgan on the X chromosome in Drosophila.
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