Genetics

Chapters

9-1 & 9-2

Incomplete dominance

• There is no dominant allele or recessive allele

• The 2 alleles are blended and make up a new physical appearance

• Ex. A red allele and a white allele can make a pink flower

Incomplete Dominance:Punnett Square Problems

• Mouth size: large mouth (L) and small mouth (l) display incomplete dominance

• Phenotype:

• large mouth male X small mouth female

• Genotype:– Male _____ X Female ______

F1 Punnett Square

– F1 genotype ratio

– F1 phenotype ratio

Incomplete Dominance:Punnett Square Problems

• Hair: curly hair (C) and straight hair (c) display incomplete dominance

• Phenotype:

• straight hair male X wavy hair female

• Genotype:– Male _____ X Female ______

F1 Punnett Square

– F1 genotype ratio

– F1 phenotype ratio

Codominance

• There is no dominant or recessive allele but both are expressed

• Ex: a chicken with white

feathers mates with a

chicken with black feathers

and they have offspring with black and white feathers

Multiple Alleles

• Traits are controlled by more than two alleles

• Example: human blood type– A (dominant)– B (dominant)– O

• AA, AO, BB, BO, OO, AB

Multiple Gene

• Polygenic Inheritance: group of gene pairs act together to produce a single trait

• Example: human eye color, height, weight, body build, eye shape, lip shape, ear shape, hair color, skin color

Pedigree

• A diagram representing a family tree

• The alleles that each person in the family has

• Males = squares

• Females = circles

• Shaded = homozygous

• Half-shaded = heterozygous