1 / 11

Extensions to Mendel: Complexities in Relating Genotype to Phenotype

Extensions to Mendel: Complexities in Relating Genotype to Phenotype. Outline of extensions to Mendel’s analysis. Single-gene inheritance In which pairs of alleles show deviations from complete dominance and recessiveness In which different forms of the gene are not limited to two alleles

santo
Download Presentation

Extensions to Mendel: Complexities in Relating Genotype to Phenotype

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. Extensions to Mendel: Complexities in Relating Genotype to Phenotype

  2. Outline of extensions to Mendel’s analysis • Single-gene inheritance • In which pairs of alleles show deviations from complete dominance and recessiveness • In which different forms of the gene are not limited to two alleles • Where one gene may determine more than one trait • Multifactorial inheritance in which the phenotype arises from the interaction of one or more genes with the environment, chance, and each other

  3. Dominance is not always complete • Crosses between true-breeding strains can produce hybrids with phenotypes different from both parents • Incomplete dominance • F1 hybrids that differ from both parents express an intermediate phenotype. Neither allele is dominant or recessive to the other • Phenotypic ratios are same as genotypic ratios • Codominance • F1hybrids express phenotype of both parents equally • Phenotypic ratios are same as genotypic ratios

  4. Three Different Forms of Dominance

  5. Incomplete Dominance for Flower Color in Snapdragon

  6. Codominance of Spotted and Dotted Coat Pattern Alleles

  7. Codominance of IA and IB Blood Group Alleles

  8. There Are Often More Than Two Alleles of a Gene The ABO blood group system is determined by one gene with three alleles.

  9. There Are Often More Than Two Alleles of a Gene Note that the ABO blood system shows both complete dominance and codominance.

  10. Multiple Alleles Can be Grouped in a Dominance Series Dominance series for lentil bean coat color.

  11. Do variations on dominance relations negate Mendel’s law of segregation? • Dominance relations affect only the relationship between genotype and phenotype • Alleles still segregate randomly and unite randomly • Gene products control expression of phenotypes • Interpretation of phenotype/genotype relationship can be complex

More Related