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 cannot be the cause because individual 2 does not exhibit the disease, yet has affected offspring. A mutation in an unaffected parent would not ensure transmission of the dominant trait.
Step 2
A germ-line mutation in individual 4
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A germ-line mutation in individual 4 is a plausible cause since individual 4 is affected and could have passed the mutation to their children. This aligns with the inheritance pattern seen in the pedigree.
Step 3
A somatic mutation in individuals 1 and 2
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A somatic mutation in individuals 1 and 2 would not be the cause as this type of mutation occurs in non-germline cells and cannot be passed on to offspring.
Step 4
A somatic mutation in individuals 4 and 5
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A somatic mutation in individuals 4 and 5 also cannot explain the presence of the genetic disease in the offspring, as somatic mutations are not heritable and would not lead to the observed inheritance pattern.
