Photo AI
Sickle cell disease is caused by a change in one of the bases coding for an amino acid on chromosome 11 - Edexcel - GCSE Biology - Question 4 - 2016 - Paper 1
Question 4
Sickle cell disease is caused by a change in one of the bases coding for an amino acid on chromosome 11. (a) Complete the sentence by putting a cross (X) in the box... show full transcript
Worked Solution & Example Answer:Sickle cell disease is caused by a change in one of the bases coding for an amino acid on chromosome 11 - Edexcel - GCSE Biology - Question 4 - 2016 - Paper 1
Step 1
Step 2
(i) Complete the genetic diagram to show the possible genotypes from two heterozygous parents.
Answer
In the genetic cross of two heterozygous parents (Ff x Ff), the possible genotypes are:
- FF (homozygous dominant)
- Ff (heterozygous, carrier)
- Ff (heterozygous, carrier)
- ff (homozygous recessive, has sickle cell disease)
The completed diagram would show the following offspring proportions: 25% FF, 50% Ff, and 25% ff.
Step 3
(ii) Calculate the percentage probability that the offspring will be carriers of the sickle cell allele but not have sickle cell disease.
Answer
To find the percentage probability that the offspring are carriers (Ff) and do not have sickle cell disease (ff), we take into account the genotypes:
- Ff (carrier, no disease) = 50%
- ff (has disease) = 25%
Thus, the probability that an offspring will be a carrier (Ff) is 50%. Therefore, the percentage probability that the offspring will be carriers of the sickle cell allele but not have sickle cell disease is:
.