Sheala and Zolton are thinking of having children together, but they are worried
ID: 21863 • Letter: S
Question
Sheala and Zolton are thinking of having children together, but they are worried. Both of them have siblings who died in their teens from a disease called cystic fibrosis, which is an autosomal (non-sex-linked) recessive disorder. Sheala also had a cousin who died at age 10 from Duchenne muscular dystrophy (DMD), a recessive X-linked disease. ON top of all of this, both Sheala and Zoltan have thalassemia minor. Given this unfortunate genetic background, both prospective parents go for genetic testing, te results of which indicate that both are carriers for cystic fibrosis. In addition, Sheala is a carrier for DMD.
a.) What is the probability that a child born to Sheala and Zoltan would have at least one of the three diseases, cystuc fibrosis, DMD or thalassemis major?
b.) Would your answer change if you knew the sex of the child?
Explain all in detail please.
Explanation / Answer
Sheala and Zolton are thinking of having children together, but they are worried. Both of them have siblings who died in their teens from a disease called cystic fibrosis, which is an autosomal (non-sex-linked) recessive disorder. Sheala also had a cousin who died at age 10 from Duchenne muscular dystrophy (DMD), a recessive X-linked disease. ON top of all of this, both Sheala and Zoltan have thalassemia minor. Given this unfortunate genetic background, both prospective parents go for genetic testing, te results of which indicate that both are carriers for cystic fibrosis. In addition, Sheala is a carrier for DMD.
called cystic fibrosis-------ALLELE------------a
normal ALLELE------------------------A
from Duchenne muscular dystrophy (DMD), a recessive X-linked---------------xr
thalassemia minor----- ALLELE-----------t
normal ----- ALLELE-----------T
both are carriers for cystic fibrosis
genotype ------ Sheala---------------Aa xr x Tt
genotype ------ Zolton ---------------Aa XY Tt
a.) What is the probability that a child born to Sheala and Zoltan would have at least one of the three diseases, cystuc fibrosis, DMD or thalassemis major?
Sheala- Aa xr x Tt X Zolton Aa XY Tt
Aa X Aa
RECEESIVE HOMOZYGOYE----AFFECTED----1/4
xr x X XY
X
Y
xr
X xr
Y xr
X
X X
YX
AFFECTED- X LINKED ---1/4
Tt X Tt
RECEESIVE HOMOZYGOYE----AFFECTED----1/4
TOTAL =1/4 X1/4 X1/4= 1/64
b.) Would your answer change if you knew the sex of the child?
AFFECTED MALE =1/64
AFFECTEDFE MALE = TOTAL =1/4 X1 X1/4= 1/16
X
Y
xr
X xr
Y xr
X
X X
YX
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