Maple syrup urine disease (MSUD) is a rare inherited human condition - AQA - GCSE Biology - Question 1 - 2022 - Paper 1
Question 1
Maple syrup urine disease (MSUD) is a rare inherited human condition.
The allele for MSUD is recessive.
What is a recessive allele?
Tick (✓) one box.
An allele e... show full transcript
Worked Solution & Example Answer:Maple syrup urine disease (MSUD) is a rare inherited human condition - AQA - GCSE Biology - Question 1 - 2022 - Paper 1
Step 1
What is a recessive allele?
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Answer
A recessive allele is an allele that is expressed only if an individual possesses two copies of it. Therefore, the correct answer to tick is:
An allele expressed only if a person has two copies of the allele.
Step 2
The symbol ▢ is not in the key for Figure 1.
What would this symbol represent?
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Answer
This symbol likely represents a male individual affected by MSUD, as it is not found in the key and usually denotes a condition or disorder.
Step 3
Complete Figure 2 to show the possible genotypes of the children.
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Answer
To complete Figure 2, we assign the following genotypes:
Person 1 (with MSUD): nn
Person 2 (without MSUD): NN
Possible offspring genotypes:
NN (not have MSUD)
Nn (carrier)
nn (have MSUD)
The combinations are:
N (from Person 2) x N (from Person 2) = NN
N (from Person 2) x n (from Person 1) = Nn
n (from Person 1) x n (from Person 1) = nn
Step 4
Which scientific term describes the allele N?
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Answer
The allele N is described as dominant, as it expresses the trait of not having MSUD when present.
Step 5
What chemical substance are alleles made from?
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Answer
Alleles are made from DNA (deoxyribonucleic acid), which is the genetic material found in the nucleus of cells.
