Complex Patterns of Inheritance

Complex patterns of Inheritance

mendelian Genetics· Mendel studied dominant/recessive alleles· many genes do NOT interact this way· some alleles are neither dominant nor recessive· many traits are controlled by different inheritance patterns

Incomplete Dominance· one allele is NOT completely dominant over another· heterozygous form looks like an in-between or blended form of the parents· in other words...there are 3 different phenotypes· example: carnations

cross red carnations with white carnation and the offspring are all PINK

Which allele is dominant? NEITHER ONE!!!

· BOTH alleles are dominant· BOTH alleles contribute to the phenotype· the heterozygous form has BOTH traits· Example #1: chickens

black chicken x white chicken = speckled chicks (both black and white)

Codominance

x =

Codominance - Example #2: Cows· if a red-haired cow is bred with a white-haired bull, all the offspring are roan (a light red)· if you look at the hairs up close with a magnifying glass, you will see that some of the hairs are actually red and white mixed· the allele for red hair and the allele for white hair are equally dominant· BOTH colors are present at the same time

X =

X

Roan Roan

25% red 50% Roan 25% White

Complex Patterns of Inheritance

Codominance & Multiple Alleles (ABO Blood groups)

· many genes can have more than one allele...or multiple alleles· this does not mean that the individual can have more than 2 alleles (1 dad, 1 mom) but it does mean that more than 2 alleles can exist in a population· Example: ABO blood group

ABO Blood Groups· multiple alleles: IA, IB, i· allele IA and IB produce a protein called an antigen on red blood cells· allele i is recessive and does not produce an antigen· someone that is IAIA or IAi will have type A blood· someone that is IBIB or IBi will have type B blood· someone that is IAIB (codominant) will have type AB blood because the body will produce BOTH antigens· someone that is ii will have type O blood and the body will make neither antigen

ABO Blood Practice Cross #1

2. Courtney also has type A blood. What are the 2 possible genotypes for Courtney?

3. Tony is actually homozygous A and Courtney is heterozygous A. What are the possible genotypes and phenotypes (blood types) for their children?

1. Tony has type A blood. What are the 2 possible genotypes for Tony?

ABO Blood Practice Cross #21. Richard has type O blood. What Richard's genotype?

2. Jenny has type A blood. What are the possible genotypes for Jenny?

3. Richard and Jenny have children. What are the possible blood types (phenotypes) and genotypes of their offspring?

ABO Blood practice Cross #3

1. Bob has type A blood. What are the possible genotypes for Bob?

2. Sheila has type B blood. What are the possible genotypes for Sheila?

3. Bob and Sheila have children. What are the possible blood types (phenotypes) and genotypes of their offspring?

Polygenic Inheritance· two or more genes control a phenotype· many human physical traits are polygenic

many phenotypes have several alleles (options) instead of two like Mendel studied· examples: hair, eye and skin color, height, weight, intelligence

Complex Patterns of Inheritance

Polygenic Inheritance Graph· polygenic traits create a bell-shaped graph