Question

question 14 part 1 Tay-Sachs disease is lethal disorder caused by a recessive mutation, in this...

question 14

part 1

Tay-Sachs disease is lethal disorder caused by a recessive mutation, in this case at the TS locus in humans. TS/TS and TS/ts genotypes do not show symptoms of the disease; however, by the age of 6 months, ts/ts infants begin to regress, usually dying by the age of five. No cure is known for Tay-Sachs.

Tay-Sachs most commonly strikes people from relatively small, closed societies, specifically those of eastern European Jewish (Ashkenazy Jews) and Louisiana (US) Cajun descent.

In the general population, the observed frequency of the ts ALLELE is 0.003 (3 x 10-3). However, in populations of Ashkenazy Jews and Cajuns, the observed frequency of the ts ALLELE is 10 times greater, or 0.03 (3 x 10-2).

Among the offspring from two parents, both of whom are CARRIERS of Tay-Sachs disease, what is the expected fraction of offspring which are carriers, and what it is the expected fraction of offspring which have the disease?

Group of answer choices

a.) Carriers: ½; Diseased: ¼

b.) Carriers: ½; Diseased: ½

c.) Carriers: 0; Diseased: ½

d.) Carriers: ½; Diseased: 0

e.) Carriers: ¾; Diseased: ¼

Homework Answers

Answer #1

Correct option A

Tay- sachs disease is rare disease which affects the nerve cells of CNS and the inheritance pattern of this disease is autosomal recessive.

Now as according to the question both the parents are carriers of this disease but they are not affected hence their genotype will be (TS ts) respectively. When they reproduce, the following cases will be there

Parent 1( TS ts ) * Parent 2(TS ts ) => following 4 cases

Case 1 - TS TS (Normal)

Case 2- TS ts (carrier)

Case 3 -TS ts (carrier)

Case 4 - ts ts (affected)

Hence 2 out of 4 are carriers i.e 1/2 are carriers and 1 out of 4 is diseased i.e 1/4.

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