Ectrodactyly, also known as “lobster claw syndrome”, can sometimes be caused by

Question

Ectrodactyly, also known as “lobster claw syndrome”, can sometimes be caused by an arginine to histidine mutation (R279H) at the p63 gene (South et al. 2002). South and colleagues sequenced a woman, her father, and son, all of whom had had the syndrome and were heterozygous for the R279H mutation at the p63 gene. Assuming that all other individuals in this woman’s family did not carry the allele,

a. What is the probability that one of her next two children will have the syndrome but not both?

b. What is the probability that 2 of her next 3 children have the syndrome?

Explanation / Answer

Ectrodactyly is a autosomal dominant condition.

E - dominant alllele for Ectrodactyly and

e - recessive allele Ectrodactyly

a. Consider the genotype of mother is Ee and the genotype of father is Ee (because no other than the given family members are affected by the disease). If the woman marries a person wth genotype "ee" then the genotype of offspring would be ee (normal individual), ee (normal individual). Ee (affected individual) and Ee (affected individual).

a. The probability that one of her next two children will have the syndrome but not both is 50%.

b.   The probability that 2 of her next 3 children have the syndrome is either 0% or 100%.

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