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From the pedigree it is reasonable to conclude that A - VCE - SSCE Biology - Question 15 - 2010 - Paper 1
Question 15
From the pedigree it is reasonable to conclude that A. II 4 is homozygous normal at the DMD locus. B. I 1 is heterozygous with respect to the DMD allele. C. I ... show full transcript
Worked Solution & Example Answer:From the pedigree it is reasonable to conclude that A - VCE - SSCE Biology - Question 15 - 2010 - Paper 1
Step 1
A. II 4 is homozygous normal at the DMD locus.
Answer
To evaluate this statement, we need to analyze the pedigree. If II 4 has affected offspring but none of his or her parents are affected, then it is possible that II 4 is homozygous normal. However, without the specific details from the pedigree, we cannot conclusively determine this.
Step 2
B. I 1 is heterozygous with respect to the DMD allele.
Answer
If we observe that I 1 has affected children, it suggests that I 1 could be heterozygous for the DMD allele. For DMD to manifest in offspring, one parent must carry at least one copy of the mutated gene, making this statement reasonable.
Step 3
C. I 1 and 2 have a one-in-four chance of producing a daughter with DMD.
Answer
This statement would be true if both I 1 and I 2 are carriers of the DMD allele. The probability of a child being affected is calculated based on the genotype of the parents. Assuming both are carriers, the chance for a female child to inherit two mutated alleles (one from each parent) is indeed 1 in 4.
Step 4
D. II 4 and 5 have a one-in-three chance of producing a daughter who is a carrier of DMD.
Answer
If II 4 is normal (homozygous) and II 5 is a carrier, their daughter would have a 50% chance of being a carrier. However, if II 4 is also a carrier, the chance increases. To conclude this statement based on the pedigree details is speculative without seeing if II 4 carries the allele.