theaero
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Three genes, D1, D2 and D3 are involved in ear formation. Homozygosity for a mutant
allele (m) at any one of these three genes will cause deafness through the elimination of a
critical component of the developing ear. In addition, homozygosity for all three genes
causes prenatal lethality resulting in spontaneous abortion of the fetus. A married couple,
both of whom are deaf, wish to have children. If the genotypes of the parents are as
indicated below, what is the likelihood that their first child will have normal hearing?
Mother: D1+/D1m, D2+/ D2m, D3m/D3m X Father: D1m/D1m, D2+/ D2m, D3+/D3m
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| son64
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0.1875
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| anjushree
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ans-1/2 *3/4 *1/2 = 0.1875
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| msyamp
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wow good one. anju you are great
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| Geroo
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agree with the answer
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| gogetit
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can one of u explain to me pls...
heres how i did it.... its given that
Mother: D1+/D1m, D2+/ D2m, D3m/D3m
Father: D1m/D1m, D2+/ D2m, D3+/D3m
now take each allele and cross....
D1+/D1m X D1m/D1m, we get D1+D1m, D1mD1m, D1+D1m, D1mD1m... so chance of homozygosity is 1/2
D2+/ D2m X D2+/ D2m, we get D2+D2+, D2+D2m, D2+D2m, D2mD2m.... so chance of homozygosity is 1/4
D3m/D3m X D3+/D3m, we get D3mD3+, D3mD3m, D3mD3+, D3mD3m..... so chance of homozygosity is 1/2
So finally its 1/2 X 1/4 X 1/2 = 1/16.......
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| gogetit
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and also what about the chance of prenatal lethality ??/ how to calculate that one?? i am lost.... pls help
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| msyamp
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hey man. he is asking the normal listening child. so if you take hozygous for any allele he will be deaf. and more over you have caluculated hoozygous for all three alleles. so you got the probabilty of a dead fetus as said in the q.
now you caluculate the heterozygous probabilty for each and multiply.you wil get probability of a health child. ok?
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| gogetit
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ok thanks mysamp... i got the heterozygus probability.... 1/2 X 3/4 X 1/2 = 3/16, but dont u need to subract 1/16.. for the chance of prenatal lethality...i am confused
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| pocas
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the question ask yu about the health children no ask yu prenatal lethality, so focus in the heterozigotes children of each allele
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| msyamp
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again substract? you are not counting the probability of all three homolugous diseased(prenataal lethal case) that is why you are getting 1/2 and 3/4 and 1/2
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