New Generations

Year 10, Pathway C

2012

Two types of inheritance

Inheritance

Intermediate Dominant/recessive

Offspring can show a mixture of both characteristics

Offspring will show one characteristic or the other. NOT a mixture of the two.

Inheritance – Dominant/recessive

Dominant/recessive inheritance - Offspring will show only one of the characteristics of the parents (eg: either brown or blue eyes, not a mixture)

This type of inheritance has one dominant allele (capital letter) and one recessive allele (lower case letter)

BCapital indicates a dominant allele

bLowercase indicates a recessive allele

BBBB results in brown eyes

bbbb results in blue eyes

BBb results in brown eyes as B dominates b

b

Inheritance – Dominant/recessive

Parent genotype: Bb Bb Parent phenotype: Brown

Brown Parent gametes: B b

B b Offspring: BB Bb

Bb bb

How many offspring have brown eyes? How many blue?

What are the genotypes of the F1 generation for the dominant/recessive eye colour gene?

Inheritance – Dominant/recessive

Offspring: BB Bb Bb bb

Genotypic ratio: ratio of the different genotypes

Eg: ¼ BB: ½ Bb: ¼ bb

Phenotypic ratio: ratio of the physical appearance

Eg: ¾ Brown: ¼ Blue