Bob and Brenda are both heterozygous for a genetically inherited recessive trait. (a) Calculate the probability that they would have a healthy child. Use a genetic diagram to help. (b) Suggest an example of a recessive inherited disorder

Heterozygous means that the parents both carry a dominant allele (A) and a recessive allele (a).

Dominant alleles are always expressed in the phenotype. Recessive alleles are expressed in the phenotype only if two recessive (a) alleles are present (one from the mother and one from the father).

For recessive disorders:

If a child inherits one dominant (A) allele and one recessive (a) allele, they are carrier for a recessive disorder.

If a child inherits two recessive (a) alleles, they will have the disease.

A             a

A             AA          Aa

a              Aa           aa

a) Probability of a healthy child= ¼ or 25%

b) Example of a recessive trait= Cystic Fibrosis/ Sickle-Cell disease/Tay-Sachs disease

CM
Answered by Charlotte M. Biology tutor

2595 Views

See similar Biology GCSE tutors

Related Biology GCSE answers

All answers ▸

Why will a plant wilt if it is not watered?


If x = 3, what is the value of 2x^2


Draw a punnet square between two carriers of cystic fibrosis and from this, work out the odds of their child being affected with CF.


How do I answer long answer questions on (eg.) diffusion/active transport/osmosis


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences