Question

In two separate Punnett squares explain the possible outcomes for the children of two different sets of parents as follows: Set A parents are both carriers of polycystic kidney disease, Set B only one parent is a carrier of polycystic kidney disease.

Explain your answer:

Answer 1

Representation:

• Polycystic kidneys to infants are transmitted as autosomal recessive trait

Normal genotype= PP

Carrier =Pp

Affected= pp

1. First condition: Both parents are carriers:

Cross: Pp x Pp

	P	p
P	PP	Pp
p	Pp	pp

Phenotype ratio:

Normal: affected = 3: 1

Genotype:

Normal = PP = ¼

Carrier = ½

Affected = ¼

2. Second condition: One parent is carrier:

Cross: Pp x PP

	P	P
P	PP	PP
p	Pp	Pp

Phenotype: All normal

Genotype:

Normal = PP = 1/2

Carrier = ½