Trait Genotype Phenotypic Effect Relationship Human Tay-Sachs Disease T_ No dise
ID: 208212 • Letter: T
Question
Trait
Genotype
Phenotypic Effect
Relationship
Human
Tay-Sachs Disease
T_
No disease
T>t
tt
Tay-Sachs Disease
MG-7: Tay-Sachs disease is a serious neurodegenerative disorder occurring in individuals homozygous for a recessive allele, t.
a. Mr. and Mrs. D are both unaffected by Tay-Sachs disease and have both a daughter with symptoms of this disease and a normal son (Son D). What is the probability that Son D is a carrier of the recessive allele?
b. Ms. E is unaffected by Tay-Sachs disease but has a brother with the disease. If Son D marries Ms. E, what is the probability that their first offspring will be affected by Tay-Sachs disease?
c. If Son D and Ms. E have four children, what is the probability that two would be affected by Tay-Sachs disease and two would be unaffected?
d. If the first offspring of Son D and Ms. E is an unaffected female, what is the probability that the second child of this marriage would be an unaffected male?
e. If the first child born to Son D and Ms. E is affected by Tay-Sachs disease, what is the probability that their second child would be affected by Tay-Sachs disease?
f. If the first child born to Son D and Ms. E is an affected female, what is the probability that the second child will be an affected male and that the third child will be an unaffected male?
Final answers provided by professor: a) 2/3, b) 1/9, c) 384/6561, d) 4/9, e) 1/4, f) 3/64
Trait
Genotype
Phenotypic Effect
Relationship
Human
Tay-Sachs Disease
T_
No disease
T>t
tt
Tay-Sachs Disease
MG-7: Tay-Sachs disease is a serious neurodegenerative disorder occurring in individuals homozygous for a recessive allele, t.
a. Mr. and Mrs. D are both unaffected by Tay-Sachs disease and have both a daughter with symptoms of this disease and a normal son (Son D). What is the probability that Son D is a carrier of the recessive allele?
b. Ms. E is unaffected by Tay-Sachs disease but has a brother with the disease. If Son D marries Ms. E, what is the probability that their first offspring will be affected by Tay-Sachs disease?
c. If Son D and Ms. E have four children, what is the probability that two would be affected by Tay-Sachs disease and two would be unaffected?
d. If the first offspring of Son D and Ms. E is an unaffected female, what is the probability that the second child of this marriage would be an unaffected male?
e. If the first child born to Son D and Ms. E is affected by Tay-Sachs disease, what is the probability that their second child would be affected by Tay-Sachs disease?
f. If the first child born to Son D and Ms. E is an affected female, what is the probability that the second child will be an affected male and that the third child will be an unaffected male?
Final answers provided by professor: a) 2/3, b) 1/9, c) 384/6561, d) 4/9, e) 1/4, f) 3/64
Explanation / Answer
a. Cross between carrier parents-
Rr x Rr
Unaffected carrier: 2/3
b. If carrier son D marries unaffected Ms. E:
Rr x Rr
Chances that the child will be affected by the disease is 1/4
.
R r R RR (Unaffected) Rr (Unaffected carrier) r Rr (unaffected carrier) rr (Affected)Related Questions
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