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Ch 5 Gene Interactions

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

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Ch 5 Gene Interactions

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

  8. ½ ML ½ M X ½ ML ½ M 2/3 tailless + 1/3 tails Manx cat ML = tailless, lethal in homozygote M = tail Tailless male x Tailless female MLM x MLM ¼ MLML ¼ MLM dies tailless ¼ MM ¼ MLM tailless tail

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

  10. Gene Interaction and the Chicken’s Comb R_P_ rrP_ R_pp rrpp

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

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

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

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

  15. Sex-Influenced Traits Androgenic alopecia

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

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

  18. Cytoplasmic DNAextensive phenotypic variation

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

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

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

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

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

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