Question

EXTRA POINTS!!!! Cystic fibrosis is regulated by a recessive allele, c. Explain (do not just fill in the Punnet square below) how two normal parents can produce a child with this disorder. Be sure to include the genotype of a child with cystic fibrosis. (Hint: give the genotypes of the normal parents and show that a cross is possible to result in a cystic fibrosis offspring).

Answer 1

Here, Assume, the parents are normal means, they aren't diagnosed with that disease. Let the Genotype of Female parent is XcX, it means, she is carrier of that disease. and Let male parent has genotype XY, it means, he is normal.

Cross: Xc X     ×     X Y

F1 Offspring: Xc X, Xc Y, XX, XY

Here, Xc Y would be the child with that disease. As "Cystic Fibrosis" is a recessive disease, it will show in a male when there is 1 copy on either gene, but in female, she must have both genes.

Genotype of Child with Cystic Fibrosis:  Xc Y

Hope this helps!