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#1
06-07-2010
 USMLE Forums Scout Steps History: --- Posts: 26 Threads: 10 Thanked 108 Times in 9 Posts Reputation: 118
Probability Calculation

The Probability of affected childrens when both parents suffer from Tay Sachs Disease is?
a-25%
b-50%
c-75%
d-100%

Plz Help i'm never able to calculate such question!!

#2
06-07-2010
 USMLE Forums Scout Steps History: Not yet Posts: 14 Threads: 4 Thanked 1 Time in 1 Post Reputation: 11
something strange Question !

Tay-Sach Dz is AR.
since the couple is Tay-Sach, the result of inheritance will be 100 %. I think, if wrong, correct me and explain.
normal inheritance is 25 %, rite ?
#3
06-07-2010
 USMLE Forums Scout Steps History: Not yet Posts: 51 Threads: 2 Thanked 32 Times in 14 Posts Reputation: 42

Yup should be 100%... both parent's genotype must be homozygous recessive thus the only alleles they have to give are mutated.

#4
06-07-2010
 USMLE Forums Guru Steps History: --- Posts: 487 Threads: 69 Thanked 296 Times in 133 Posts Reputation: 316

by calculation... there is 100% chance of having disease...
but guys..do u think that if a child is having tay sachs disease, will grow to adult to hv his own child!!!
if they r suffering from disease...means having both mutated allele...most probably they cant live for more then 5 yrs???
#5
06-07-2010
 USMLE Forums Addict Steps History: 1+CK+CS Posts: 122 Threads: 6 Thanked 39 Times in 27 Posts Reputation: 49

Answer is "D" 100% probability since Taysach is Autosomal recessive ... And both parents are affected.
-If one of the parents is affected & the other is normal, the answer will be zero but all children will be carriers.
-If both are carriers, the answer will be 25%. If one of parent is carrier and the other is affected.
-If one is carrier & other parent is affected, the answer will be 50% risk with teh otehr 50% carrier children.

 Tags Genetics-, Step-1-Questions

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