Question

I need help please with this I need to make a punnet square to prove my pedigree

Answer 1

In this case, Cystic fibrosis is generated by a recessive allele, which means that both copies must be recessive to present the disease, on the contrary, if one allele is dominant and the other recessive the person will be a carrier but it won't show the disease, and a completely healthy person will be a dominant homozygous, so even when Joshua and Bella are healthy, both are carriers which is the punnet square we will show here.

Alleles

A: Dominant, healthy

a: recessive, CF

Parental cross:

Aa x Aa

Punnet square:

`\begin{bmatrix}{\placeholder{⬚}} & A & {a} \\ {A} & {AA} & {Aa} \\ {a} & {Aa} & {aa}\end{bmatrix}`

Frequencies

Phenotypic: 3:1 = 75% healty, 25% CF

Genotypic: 1:2:1 = 25% homozygous dominant, 50% Heterozygous carrier, 25% Homozygous recessive CF.

Next we have the matching pedegree