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Figure 8 shows an image of a small section of DNA - AQA - GCSE Biology - Question 7 - 2018 - Paper 1
Question 7
Figure 8 shows an image of a small section of DNA. Figure 9 shows the structure of a small section of DNA. 1. What is Part B? 2. In Figure 8 the structure of DNA s... show full transcript
Worked Solution & Example Answer:Figure 8 shows an image of a small section of DNA - AQA - GCSE Biology - Question 7 - 2018 - Paper 1
Step 1
Step 2
Step 3
Explain how the mutation could cause the enzyme not to work.
Answer
The mutation results in a change from C to T in the DNA code, altering the triplet from CAG to TAG. This mutation leads to a change in the amino acid sequence of the protein produced by the enzyme IDUA. As a result, the enzyme may fold into a different structure, resulting in an altered active site that cannot effectively bind with its substrate, rendering the enzyme inactive.
Step 4
Draw a Punnett square diagram to determine the probability of the child having syndrome H.
Answer
To determine the probability, we can set up a Punnett square:
A a
----------------
A | AA | Aa |
----------------
a | Aa | aa |
----------------
Where:
- A = Dominant allele (not having syndrome H)
- a = Recessive allele (having syndrome H)
From the above Punnett square:
- The probability of having a child with syndrome H (aa) is 1 out of 4 or 25%.