1. Ch 5 Gene Interactions Modification of Mendel’s Observations

2. Outline Penetrance versus expressivity Dominance –Variations Lethal Genes Multiple Allelic traits Gene Interaction –Epitasis Sex Influence traits Sex limited traits Cytoplasm Inheritance Genomic Imprinting Anticipation Genes and our environment

3. Polydactyly an example of:: Penetrance=% of indiduals with a genotype that express the phenotype Expressivity= Degree to which trait is expressed

4. Dominance and its variations

5. Blood type is co-dominant

6. Hierarchy Of dominance

7. 2:1 ratio 2/3 are Yy 1/3 are yy Lethal recessive LETHAL INTERACTIONS

8. Manx cat M L = tailless, lethal in homozygote M = tail Tailless male x Tailless female M L M x M L M ½ M L ½ M ½ M L ½ M ½ M L ½ M ¼ M L M L ¼ M L M ¼ MM diestailless taillesstail 2/3 tailless + 1/3 tails X

9. 2 loci but one characteristic Gene Interaction R=red r=no red color C=destroys chlorophyll c=allows for chlorophyll

11. R_P_ rrppR_pp rrP_ Gene Interaction and the Chicken’s Comb

12. Gene Interaction and Epitasis Masking of expression of one gene by another gene Epistatic genes be recessive or dominant

13. Gene Interaction and Epitasis yellow black chocolate BBEE x bbee yellow black BbEe black

14. “e” shows recessive epistasis B_E_ black bbE_ brown B_ee yellow bbee yellow 9/16 3/16 1/16 4/16 All Yellow

15. W_Y_ white squash W_yy white squash wwY_ yellow squash wwyy green squash “W” is the dominant inhibitor allele “W” shows dominant epistasis Genes proteins Enzyme pathways

16. Sex-Influenced Traits Androgenic alopecia

17. Sex Limited Traits hh Cock feathering male H_ hen feathering female Or hh hen feathering female H_ hen feathering male but

18. Sex Limited in Humans (refers specifically for an abnormal protein, LH receptor)

19. Cytoplasmic DNA extensive phenotypic variation

20. Genomic Imprinting Angelman Syndrome Different expression depending if the same autosome(s) inherited maternally or paternally. Missing part of paternal chromosme 15 Missing part of maternal chromosme 15

21. Anticipation When genetic trait becomes more strongly expressed at an earlier age.

22. Environmental Effects and Gene Expression The Himalayan Rabbit Temperature sensitive allele

23. Pleiotropic Effects (versus polygenic) One gene affects many traits

24. The End Thursday: begin reading chapter 7 through 3 pt. test cross