Is it possible to tell from the pedigree whether inheritance of the PSEN1 gene m
ID: 206115 • Letter: I
Question
Is it possible to tell from the pedigree whether inheritance of the PSEN1 gene mutation is dominant or recessive? Explain your answer.
Is it possible to tell from the pedigree whether inheritance of the PSEN1 gene mutation is autosomal or sex-linked? Explain your answer.
The PSEN1 gene mutation in this study was previously determined to be autosomal dominant. Knowing this, would the mother of the unaffected child in generation III (white square) be heterozygous or homozygous for the mutation? Explain your answer.
Give the probability of having offspring without the mutation in the following scenarios:
o One parent is homozygous for the mutation and the other parent does not have the mutation.
o One parent is heterozygous for the mutation and the other parent does not have the mutation.
o Both parents are heterozygous for the mutation.
Is it possible to determine from the pedigree when the PSEN1 gene mutation first occurred? If so, how? If not, why not?
How was it possible for the scientists to construct this pedigree when the majority of family members are deceased and their DNA is not available for analysis?
1745 1770 1790 C2 C6 C3 C4 1850 C1 C5 C11 1890 VIl 1910 VIll 1930 C12 C13 C C9 C8 C21Explanation / Answer
1) It has been determined that the PSEN1l mutation is an autosomal dominant mutation. However, this cannot be interpreted from the pedigree since the disease is prevalent throughout the family.
2) Since, the mutation is equally present in males and females, it is autosomal.
3) In the chart, it has been shown, that a female member of the family (generatin II) had two different sposes without the disease. From one of these marraiges, a child was born without having the disease. From the other marriage, a child was born with an uncertain status of the disease.
From the above outcome, it can be interpreted that the mother carried the mutation in heterozygous form.
4) when one parent is homozygous for the mutation and the other parent does not have the mutation, the probability of appearance of the disease is 100%, since only one dominant allele is required for disease appearance.
When one parent is heterozygous for the mutation and the other parent does not have the mutation, the probalilty of offspring with the mutation will be 50%
When both parents are heterozygous for the mutation, 75% of the offspring will carry the mutation.
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