The occurrence of a genetic disease in a family resulting from the presence of a dominant allele is shown - HSC - SSCE Biology - Question 18 - 2022 - Paper 1
Question 18
The occurrence of a genetic disease in a family resulting from the presence of a dominant allele is shown.
If the disease has arisen as a result of a mutation, whic... show full transcript
Worked Solution & Example Answer:The occurrence of a genetic disease in a family resulting from the presence of a dominant allele is shown - HSC - SSCE Biology - Question 18 - 2022 - Paper 1
Step 1
A germ-line mutation in individual 2
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Answer
A germ-line mutation in individual 2 is a plausible explanation since individual 2 is unaffected but has an affected offspring (individual 4). This suggests that the mutation could have been inherited.
Step 2
A germ-line mutation in individual 4
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Answer
If individual 4 had a germ-line mutation, it could explain the disease, but since individual 4 is affected, it suggests that they inherited the mutation rather than caused it.
Step 3
A somatic mutation in individuals 1 and 2
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Somatic mutations typically do not affect offspring since they occur in non-germ-line tissues. Therefore, this option is less likely to explain the hereditary nature of the disease.
Step 4
A somatic mutation in individuals 4 and 5
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Similar to option C, somatic mutations cannot be passed to offspring. Therefore, they cannot be the reason for the genetic disease's appearance in the family.
