1 / 25

Non-Mendelian Genetics

This review covers non-Mendelian genetics, including the concepts of dominant and recessive alleles, as well as incomplete dominance, codominance, multiple alleles, polygenic traits, and sex-linked traits. Examples and cross calculations are provided to illustrate these concepts.

vbrandt
Download Presentation

Non-Mendelian Genetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Non-Mendelian Genetics

  2. phenotype: purple phenotype: white phenotype: purple Mendelian Genetics: Dominant & Recessive Review • One allele is DOMINANT over the other (because the dominant allele can “mask” the recessive allele) genotype: PP genotype: pp genotype: Pp

  3. PP Pp Pp pp 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 GENOTYPES: - PP (25%) Pp (50%) pp (25%) - ratio 1:2:1 P p PHENOTYPES: - purple (75%) white (25%) - ratio 3:1

  4. Non-Mendelian Genetics • Incomplete Dominance • Codominance • Multiple Alleles • Polygenic Traits • Sex-Linked Traits

  5. RR = red rr = white Rr = pink Incomplete Dominance • a third (new) phenotype appears in the heterozygouscondition as a BLEND of the dominant and recessivephenotypes. Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr)

  6. R r r r Rr Rr rr rr Problem: Incomplete Dominance • Show the cross between a pink and a white flower. GENOTYPES: - RR (0%) Rr (50%) rr (50%) - ratio 1:1 PHENOTYPES: - pink (50%); white (50%) - ratio 1:1

  7. NS = some of each SS = sickle cells NN = normal cells 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 - sick

  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. NS SS SS NS Problem: Codominance • Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S GENOTYPES: - NS (50%) SS (50%) - ratio 1:1 S S PHENOTYPES: - carrier (50%) sick (50%) - ratio 1:1

  13. Multiple Alleles • there are more than twoalleles 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. Ai Ai Bi Bi Problem: Multiple Alleles • Show the cross between a mother who has type O blood and a father who has type AB blood. GENOTYPES: i i - Ai (50%) Bi (50%) - ratio 1:1 A B PHENOTYPES: - type A (50%) type B (50%) - ratio 1:1

  19. Bi AB Ai ii 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. GENOTYPES: A i • AB (25%); Bi (25%); Ai (25%); ii (25%) - ratio 1:1:1:1 B i PHENOTYPES: • type AB (25%); type B (25%) type A (25%); type O (25%) - ratio 1:1:1:1

  20. Polygenic Traits • traits produced by multiple genes • example: skin color

  21. 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, hemophilia

  22. 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.

  23. 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

More Related