Please show the working to how to get the answer Two genes A

Please show the working to how to get the answer.

Two genes A and B work in sequence to give rise to the Agouti coat pattern in mice. Below is the sequence of steps: White precursor Black Agouti pattern If allele A = color and allele a = albino If allele B= agouti and b=black So A and B represent the functional or normal copies of the genes whereas a and b represent the non-functional or defective copies of the genes. If you cross two individuals with the genotype what proportion of the progeny would be expected to be albino: 9/16 3/16 1/16 1/4 1/64

Solution

AaBb      X       AaBb ..................................................................Parent

AB

Ab

aB

ab

AB

AABB

AABb

AaBB

AaBb

Ab

AABb

AAbb

AaBb

Aabb

aB

AaBB

AaBb

aaBB

aaBb

ab

AaBb

Aabb

aaBb

aabb

..............Progeny

Now the phenotype, genotype and their ratio of the above progeny :

Phenotype

Genotype

Genotype ratio

Phenotype ratio

Color Agouti

AABB

AABb

AaBb

AaBb

1

2

2

4

9

Color Black

AAbb

Aabb

1

2

3

Albino Agouti

aaBB

aaBb

1

2

3

Albino Black

Aabb

1

1

Here we can see that out of 16 progeny albino progeny will be – 4

So, the proportion of expected albino progeny will be – 4/16 = ¼.

The ans will be 4.

	AB	Ab	aB	ab
AB	AABB	AABb	AaBB	AaBb
Ab	AABb	AAbb	AaBb	Aabb
aB	AaBB	AaBb	aaBB	aaBb
ab	AaBb	Aabb	aaBb	aabb