1 / 13

Variations in Heredity

This educational overview explores the concepts of incomplete dominance and codominance using examples from plant and animal genetics. By examining the breeding of red and white snapdragons, we observe how a blend of traits results in pink flowers. We also discuss codominance through the inheritance of blood types in humans, demonstrating how multiple alleles produce various blood types. Learn how to construct Punnett squares to predict genotypic and phenotypic ratios in offspring, and understand the significance of these genetic interactions in real-world scenarios.

istas
Télécharger la présentation

Variations in Heredity

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. Variations in Heredity Incomplete and Codominance

  2. More Dragon Genetics… • A pure breeding red snapdragon is bred with a pure-breeding white snapdragon. What should we expect in the F1 generation? X = • What happened here? All Pink?! Huh?

  3. Incomplete Dominance • Neither colour can mask the other; so the offspring express a blend of parents’ traits. • How do we represent these alleles? • Choose a letter for the gene (colour) • Choose 2 different letters to represent each allele, both will be capitals • CR and CW

  4. Try This Red snapdragon X White snapdragon • Construct a Punnett square to determine genotype and phenotype ratios in: a) F1 generation b) F2 generation

  5. Codominance • Another type of interaction, called codominance, can occur when both of the parental alleles are expressed in the offspring at the same time. (*each trait is expressed independently; no blending)

  6. Example of Codominance Red Bull (HrHr) X White Cow (HwHw) = Roan Cow (HrHw) Roan cattle have a both red and white hairs (no pink hairs)

  7. Try This Red Bull X White Cow • Construct a Punnett square to determine genotype and phenotype ratios in: a) F1 generation b) F2 generation

  8. Codominance in Humans • Human blood type is a dominant and codominant trait. • There are 3 different blood type alleles: A, B, and O. • These alleles produce 4 possible blood types: A, B, AB, and O • The various blood types specify which proteins are present on the surface of red blood cells.

  9. O is recessive to A and B • A and B are codominant • Alleles are represented as follows: • A = IA • B = IB • O = i • Determine the possible genotypes for people with each of the 4 blood types.

  10. Rhesus Factor • The Rhesus factor is a Mendelian trait and indicated by + or – after the blood type. • In reality there are 8 possible blood types: AB +/- A +/- B+/- O +/-

  11. Monohybrid Cross Worksheet • 1. All red, all heterozygous • 2. Both are heterozygous. Alleles are B (black) and b (white) • 3. a) Alleles freckles: F no freckles: fb) no freckles ffc) freckles Ff or FF • 4. a) White recessive, black dominant b) parents: Bb x Bb Offspring: BB, Bb, bb • 5. a) RRb) Rr • 6. genotypes: ½ Dd, ½ dd phenotypes: ½ purple, ½ white • 7. Ss xss • 8. F1 – yes, all heterozygous and all show dominant trait F2 – Yes, approximate 3:1 ratio (25% TT, 50% Tt, 25% tt) • 9. Not possible to determine genotypes; could be: Bb x Bb or Bb x bb (can’t be BB x Bb or BB x bb)

  12. Blood Type: Mini Case Studies • Case 1 – Grace is adopted • Case 2 – yes, he could be the father, only if mother’s genotype is Iai • Case 3 – Possible blood types: A, B, AB, O, all have equal probability (25%) • Case 4 – A (25%), AB (50%), B (25%), O (0%) • Case 5 – Could receive blood from Rhonda and Howard (Patient has antibodies to blood from Richard or Shelly) • Case 6 – Sarah: IAi George: IBiGregor: IAi Barbara: ii Rosalind: IA IB

More Related