Alfa Thalassemia Carrier marries Beta Thalassemia Carrier! - USMLE Forums
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Old 09-21-2012
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Genetics Alfa Thalassemia Carrier marries Beta Thalassemia Carrier!

Thalassemia can be alpha and beta type...if in a population with high prevalence., what is the probability of the first child if 1 alpha thalassemia carrier marries beta thalassemia carrier..?

a) 100%
b) 75%
c) 66%
d) 50%
e) 25%
f) 0%
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Old 09-22-2012
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Default Zero percent.

Atleast 2 carriers of an autosomal recessive gene mutation must mate to form a progeny with diseased phenotype. Both the parents are carriers of 2 "different" mutations, so neitger will cause disease.
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Old 09-22-2012
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Never thought this way.
But I think it would be 0%


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Old 09-22-2012
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F--- two distinct allele
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Old 09-22-2012
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Quote:
Originally Posted by venky2600 View Post
Q) thalassemia can be alpha and beta type...if in a population with high prevalence., what is the probability of the first child if 1 alpha thalassemia carrier marries beta thalassemia carrier..?

a) 100%
b) 75%
c) 66%
d) 50%
e) 25%
f) 0%
Ans is F.ZERO...mutations causing Alpha thalessemia and BETA thalassemia are at two different loci .. all of the offspring will be heterozygous carriers of these two different mutations..to be affected with the Disease offspring must be HOMOZYGOuS FOR THE MUTATIONS
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Old 09-23-2012
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yes, the correct answer is F) 0%

explanation-----thalassemia is autosomal recessive, so need homozygous mutated gene for affecting the offspring(heterozygous can't transmit the disease).....if both heterozygous carriers(if in high prevalent population) can affect 25% disease, 50% heterozygous carriers and 25% homozygous normal

as alpha thalassemia and beta thalassemia are considered as mutation in different gene locus they can't be considered as a single disease...so each affected parent are taken into account independantly.....

here in question...1 alpha thalassemic heterozygote carrier(can transmit single mutated gene to 50% of offspring) and 1 beta thalassemic heterozygote carrier( can transmit to 50% of offspring)...but none of them would be affected with the disease
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