7. (2pt) The pedigree below shows the familial genetic history of two rare disor
ID: 47374 • Letter: 7
Question
7. (2pt) The pedigree below shows the familial genetic history of two rare disorders. Individuals in this pedigree with a dark shaded left side have Gillespie syndrome, which causes a multitude of symptoms such as aniridia (absence of the iris), ataxia (motor and coordination problems) and, in most cases, a general learning disability. Those with a dark shaded right side have polydactylism. a condition that causes a person to have additional digits. a. What is the most likely mode of transmission for each of these disorders? b. What is genotype for those in row-III? c. How could you find out the unknown genotypes from the previous question? d. If individuals IV-3 and IV-8 were to mate, what is the probability that their child would have Gillespie syndrome and polydactylism?Explanation / Answer
a. Since the trait for Gillespie syndrome and polydactylism does not skip generation and offspring is born to affected parents with equal frequency therefore, the mode of transmission for this syndrome is autosomal dominant.
b. The offsprings suffering from the disease will need to have just one dominant allele to cause the disease. While others will be homozygous recessive for the traits of disease. Thus,
While those with polydactylism will have Ppgg
Those with Gillespie syndrome will have ppGg
c. The unknown genotypes will be:
the genotype of normal offsprings in row III will be ppgg,
d. If IV-3 and IV-8 mate then the cross will be between ppGg and Ppgg
The cross will be:
pG
ppGg
From this cross we can see that 4 out of 16 offsprings will have the genotype PpGg. This means that probability that child will have Gillespie syndrome and polydactylism is 25% or 1/4.
Pg pg Pg pgpG
PpGg ppGg PpGg ppGg pg Ppgg ppgg Ppgg ppgg pG PpGg ppGg PpGgppGg
pg Ppgg ppgg Ppgg ppggRelated Questions
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