Continuing Genetics DOMINANCE Unit 5: Mendelian Genetics

Continuing GeneticsDOMINANCE

Unit 5: Mendelian Genetics

Independent Assortment• genes that are

inherited separately do not influence the inheritance of others

• Alleles segregate independently during meiosis

• some go to one gamete and some to another

Types of Dominance

Incomplete Dominance:• Offspring genotype is

heterozygous (hybrid)• Phenotype is between

two parents• In offspring, Dominant

gene cannot fully inhibit the recessive

• Ex: white flower x red flower = pink flowers

Codominance:

• Offspring shows phenotype of neither parent

• Both alleles are dominant

• Ex: black cow x white cow = checkered/spotted cow

Bay horse x white horse = roan horse

• Multiple alleles: more than two alleles control a trait

• Ex: height, hair color, eye color and blood type

Blood type inheritance• Blood type is determined by the presence or

absence of proteins on surface of red blood cells• Blood types: A, B, AB and O

Phenotype (BLOOD TYPE)

 GENOTYPE

 ANTIGEN on red

blood cell

SAFE TRANSFUSIONS

TO FROM

A  AA or AO  A  A, AB A, O

B BB or BO  B   B, AB B, O

AB Only AB  A & B   AB A, B, AB, O

O  Only OO None   A, B, AB, O O

Sex-linked alleles

• controlled by genes located on sex chromosomes

• Usually carried on X chromosome

• Since females are XX, they are usually carriers of the trait

• Since males are XY, they have a higher tendency for inheritance of trait

Sex-linked • If trait is X-linked: males pass it to all of their daughters, none to sons

• If trait is X-linked: mothers have 50/50 chance of passing it to all of their children

• Ex: colorblindness, hemophilia

• Work the following Punnett Square:

• Male: has Hemophilia (XhY)

• Female: Carrier (XHXh)