non-medelian inheritance according to mendal.pdf
- 2. Mendelian Genetics: Dominant & Recessive Review One allele is DOMINANT over the other (because the dominant allele can “mask” the recessive allele) genotype: PP phenotype: purple genotype: pp phenotype: white genotype: Pp phenotype: purple
- 3. Review Problem: Dominant & Recessive In pea plants, purple flowers (P) are dominant over white flowers (p). Show the cross between two heterozygous plants. P p P p pp Pp Pp PP - PP (25%) Pp (50%) pp (25%) - ratio 1:2:1 - purple (75%) white (25%) - ratio 3:1 GENOTYPES: PHENOTYPES:
- 4. Non-Mendelian Genetics Incomplete Dominance Codominance Multiple Alleles Polygenic Traits Sex-Linked Traits
- 5. Incomplete Dominance a third (new) phenotype appears in the heterozygous condition as a BLEND of the dominant and recessive phenotypes. Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr) RR = red rr = white Rr = pink
- 6. Problem: Incomplete Dominance Show the cross between a pink and a white flower. - RR (0%) Rr (50%) rr (50%) - ratio 1:1 - pink (50%); white (50%) - ratio 1:1 R r r r rr Rr rr Rr GENOTYPES: PHENOTYPES:
- 7. Codominance in the heterozygous condition, both alleles are expressed equally with NO blending! Represented by using two DIFFERENT capital letters. Example: Dominant Black (B) + Dominant White (W) = Speckled Black and White Phenotype (BW) Sickle Cell Anemia - NN = normal cells SS = sickle cells NS = some of each
- 8. Codominance Example: Speckled Chickens BB = black feathers WW = white feathers BW = black & white speckled feathers Notice – NO GRAY! NO BLEND! Each feather is either black or white
- 9. Codominance Example: Rhodedendron R = allele for red flowers W = allele for white flowers Cross a homozygous red flower with a homozygous white flower.
- 10. Codominance Example: Roan cattle cattle can be red (RR – all red hairs) white (WW – all white hairs) roan (RW – red and white hairs together)
- 11. Codominance Example: Appaloosa horses Gray horses (GG) are codominant to white horses (WW). The heterozygous horse (GW) is an Appaloosa (a white horse with gray spots). Cross a white horse with an appaloosa horse. W W G W GW GW WW WW
- 12. Problem: Codominance Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S S S NS NS SS SS - NS (50%) SS (50%) - ratio 1:1 - carrier (50%) sick (50%) - ratio 1:1 GENOTYPES: PHENOTYPES:
- 13. Multiple Alleles there are more than two alleles for a gene. Ex – blood type consists of two dominant and one recessive allele options. Allele A and B are dominant over Allele O (i)
- 14. Multiple Alleles: Lab Mouse Fur Colors Fur colors (determined by 4 alleles): black agouti yellow
- 15. Multiple Alleles: Rabbit Fur Colors Fur colors (determined by 4 alleles): full, chinchilla, himalayan, albino
- 16. Multiple Alleles: Blood Types (A, B, AB, O) Rules for Blood Types: A and B are co-dominant (Both show) AA or IAIA = type A BB or IBIB = type B AB or IAIB = type AB A and B are dominant over O (Regular dom/rec) AO or IAi = type A BO or IBi = type B OO or ii = type O
- 17. Multiple Alleles: Blood Types (A, B, AB, O)
- 18. Phenotype Possible Genotype(s) Allele (antigen) on RBC surface Can Donate Blood To Can Receive Blood From A IAi IAIA A A, AB A, O B IBi IBIB B B, AB B, O AB IAIB AB AB A, B, AB, O O ii O A, B, AB, O O
- 19. Problem: Multiple Alleles Show the cross between a mother who has type O blood and a father who has type AB blood. - AO (50%) BO (50%) - ratio 1:1 - type A (50%) type B (50%) - ratio 1:1 GENOTYPES: PHENOTYPES: O O A B AO BO AO BO
- 20. Problem: Multiple Alleles Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood. -AB (25%); Bi (25%); Ai (25%); ii (25%) - ratio 1:1:1:1 -type AB (25%); type B (25%) type A (25%); type O (25%) - ratio 1:1:1:1 GENOTYPES: PHENOTYPES: A i B i AB ii Bi Ai
- 21. Polygenic Traits traits produced by multiple genes example: skin color
- 22. Sex-Linked Traits Gene is attached to the X chromosome only, not found on the Y chromosome at all. (women have XX, men have XY chromosomes). These disorders are more common in boys. examples: red-green colorblindness
- 23. Sex-Linked Traits in males, there is no second X chromosome to “mask” a recessive gene. If they get an X with the disorder, they have it. Girls must inherit defective X’s from both parents.
- 25. Sex-Linked Traits A: 29, B: 45, C: --, D: 26 Normal vision A: 70, B: --, C: 5, D: -- Red-green color blind A: 70, B: --, C: 5, D: 6 Red color blind A: 70, B: --, C: 5, D: 2 Green color blind