Question

pedigree test
background information
the pedigree below shows the inheritance pattern of a genetic disease across three generations of a family. study the pedigree carefully to answer the questions.

1. mode of inheritance

based on the pedigree, determine the most likely mode of inheritance (dominant or recessive) for this genetic disease. support your answer with three specific pieces of evidence from the pedigree.
mode of inheritance:
evidence:

Explanation:

• Recessive Inheritance Evidence 1: Unaffected parents (III - 1 and III - 2) have an affected child (IV - 1). In dominant inheritance, at least one parent would need to be affected to pass on the dominant allele.
• Recessive Inheritance Evidence 2: Affected individuals (e.g., II - 2) can have unaffected siblings (II - 3, II - 4). If it were dominant, the probability of unaffected siblings would be lower as the affected individual would likely pass on the dominant allele more frequently.
• Recessive Inheritance Evidence 3: In generation IV, when an affected female (IV - 5's parentage implies she has the recessive trait) has children with an unaffected male (IV - 6), not all children are affected. In dominant inheritance, if one parent has the dominant allele, there is a higher chance of more children being affected.

Answer:

Mode of inheritance: Recessive
Evidence:

1. Unaffected parents (III - 1 and III - 2) have an affected child (IV - 1).
2. Affected individuals (e.g., II - 2) have unaffected siblings (II - 3, II - 4).
3. An affected female (IV - 5's situation) and an unaffected male (IV - 6) do not have all - affected children.