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1. Give the genotypes of the ABO blood groups for individuals 1 and 2 - AQA - A-Level Biology - Question 6 - 2022 - Paper 2
Question 6
1. Give the genotypes of the ABO blood groups for individuals 1 and 2. 1 Blood group A 2 Blood group AB 2. Explain one piece of evidence from Figure 3 that the... show full transcript
Worked Solution & Example Answer:1. Give the genotypes of the ABO blood groups for individuals 1 and 2 - AQA - A-Level Biology - Question 6 - 2022 - Paper 2
Step 1
Step 2
Explain one piece of evidence from Figure 3 that the allele for Rhesus positive is dominant.
Answer
In Figure 3, individuals with a Rhesus positive phenotype (like individuals A and AB) can produce offspring with a Rhesus negative phenotype (like individual O). This indicates that the presence of the Rhesus positive allele can mask the expression of the Rhesus negative allele.
Step 3
Calculate the probability of individuals 1 and 2 producing a Rhesus positive son with blood group A (individual 3).
Answer
To find the probability, we assume that individual 1 is heterozygous for the Rhesus blood group () and individual 2 is also (since they can produce Rhesus negative offspring).
Possible Rhesus offspring:
- (Rhesus positive)
- (Rhesus positive)
- (Rhesus positive)
- (Rhesus negative)
This results in a probability of producing a Rhesus positive child of rac{3}{4}.
Next, consider the ABO blood groups. Individual 1 can pass on either or , while individual 2 can pass on or . The combinations yielding blood group A are:
- (from individual 1) and (from individual 2)
- (from individual 1) and (from individual 2)
Thus, the probability of individual 3 being blood group A is rac{1}{4} (for homozygous) + rac{1}{4} (for heterozygous from individual 1's contribution).
Combining these, the total probability of producing a Rhesus positive son with blood group A is:
P(RR ext{ or } Rr) imes P(A) = rac{3}{4} imes rac{1}{2} = rac{3}{8}.