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#1




question_ genetics/ probability
betahexosaminidase is made up of alpha and beta subgroups. Taysachs disease is due to a mutation in the alphasubunit gene, and sandhoff disease is due to a mutation in betasubunit gene. If a carrier of taysachs disease marries a carrier of sandhoff disease, what is the probability that their first child will have either disease
A 0% B 12.5% C 25% D 50% E 100% please educate me with rationale. thanx
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#3




Quote:
because the child may inherete just one mutated allele of each gene so child will be carrier of each/both dis or will be normal 
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#4




0%
because each parent is a carrier of a different autosomal recessive disease gene subunit mutation, the child born has a 0% chance of acquiring either of the disease mentioned 
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#5




Ans  0%
Both disease are autosomal recessive  so they need 2 chromosomes to MANIFEST .... (carriers have only one defective chromosome) If carrier mother has chromosomal structure Ax (A = normal and x = gene for tay sachs) And carrier father has chromosomal structure Az (A = normal and z = gene for sandoff's) their possible offsprings will have the following structure  AA  Az  Ax  xz But to MANIFEST the disease, the chromosomal structure needs to be xx(tay sach's) or zz(sandoff)... So 0% of the offspring will MANIFEST either disease.  How many percent of their offspring willl be CARRIERS of either disease? Ans   75%  How many percent of their offspring will be CARRIERS of both diseases? Ans   25% 
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#6




why have u taken A as the normal(dominant) allele for both the diseases why should nt we consider them as separate genes pls xplain......?

#7




Devareddy has a point  HEXA and HEXB are different genes on different chromosomes (15 and 5 respectively). So, if the parents are each carriers for only one of the diseases, the probability that the child will be a carrier for either is 50%, and the probability that the child will be a carrier for both is 25%. The probability that the child will have either disease is 0% if each parent for sure only carries one disease (if the wording of the question leaves open the possibility that a parent could be a carrier unknowingly for the other, then the probability of the child having either disease is 50% of the prevalence of that allele in the general population. Both are rare diseases, so the answer is closer to 0 than to 12 in any case).

#8




Quote:
0%. 
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