lecture presdentation oif spistasis .ppt
- 1. OUTLINE 16 E. Violation of independent assortment 3. Crossing over 4. Chromosome mapping 5. Effects of linkage and crossing over on genotypic and phenotypic ratios F. Pleiotropy G. Violation of complete expression 1. Gene interaction - epistasis 2. Consequences penetrance expressivity H. Phenotypic plasticity
- 2. = centrosome P: PL//PL X pl//pl F1: (PL//pl) P P p p L L l l P p p P L L l l
- 3. Effects of crossing over on number of possible gamete types P p P p L L l l P P L L p p l l P l p L P L p l pL Pl PL pl With x-over No x-over
- 5. Test cross F1 to double recessive: Parents PpLl X ppll PL//pl X pl//pl Gametes PL pl PL parental (7) Pl pl parental (7) pL pL recombinant (1) pl Pl recombinant (1) Expect 1:1:1:1 ratio of phenotypes Bateson and Punnett observed 7:1:1:7 2/16 = 12.5% recomb.
- 6. Alfred H. “Hot Dog” Sturtevant
- 7. P L A L How do we know if it’s P- A - L , or P - L- A? If x-over frequency between P and A is 7.5% then: P A L If x-over frequency between P and A is 17.5% then: P L A 12.5 map units 7.5 map units 12.5 map units 5 map units 5 map units 5 units
- 8. Fig 15.6
- 10. Application of Mendel’s Rules assumes: 1. One allele completely dominates the other 2. All genes have 2 allelic forms 3. All traits are monogenic (affected by only one locus) 4. All chromosomes occur in homologous pairs 5. All genes assort independently 6. An allele is completely expressed when either dominant or heterozygous 7. Each trait is controlled by a different set of factors
- 11. Pleiotropy: The same locus influences coat color and crossed eyes in felines
- 12. Fig 14.11 Effect of epistasis on phenotypic ratios of a dihybrid cross C= pigment c = none B = deposition of lots of pigment (black) b = less deposition (brown) If cc, fur is white regardless of genotype at B locus
- 13. Phenotypic plasticity in Daphnia Predator absent Predator present
- 14. Crayfish predator Sunfish predator Snail prey
- 15. A snail raised with fish A full sib raised with crayfish