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Home Q & A Board Biology-Related Homework Help General Biology
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Taylor14 Taylor14
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10 years ago Edited: 10 years ago, bio_man
1. Achondroplasia, a form of dwarfism, is inherited as a dominant condition. two dwarfs, both of whom had one parent of normal height, marry and plan to a have child. Their first child is born and is a dwarf. What is the probability that this child is heterozygous?
 
2. Sally claims that Joe is the father of her child, while Joe insists he is not the father. Sally is blood type O, Joe is blood type AB and the child is blood type O. Could Joe be the father?

3. Maria has type O blood and her sister has type AB blood. The girls know that both of their maternal grandparents are type A. What are the genotypes of the girls' parents?

Can u guys help me solve these problems with punnet squares? Thanks in advance.
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10 years ago
1. the parents are heterozygous, because they inherited one recessive allele from their normal height parent (who is homozygous to the ressecive gene d)

So, the crossing is
Dd x Dd
1 DD : 2 Dd :1 dd
(D is the dominant for dwarf, d is the recessive for tall)

And, if you want punnett, here:
        D       d
D    DD    Dd
d     Dd    dd
(Again, probabilities 1:2:1)

Since the child is dwarf, it can't be dd. (Or it would be tall)
This means that the probabilities are 1DD : 2Dd
So, the child has 1/3 being DD and 2/3 being Dd.
So, your answer should be 2/3.

I'll deal with the rest tomorrow if no one else does
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10 years ago
Quote from: Taylor14 (10 years ago)
1. Achondroplasia, a form of dwarfism, is inherited as a dominant condition. two dwarfs, both of whom had one parent of normal height, marry and plan to a have child. Their first child is born and is a dwarf. What is the probability that this child is heterozygous?

0.67. The parental cross is Aa x Aa, and the Punnett square is:

_____A_____a__
A___AA____Aa__
a___Aa____aa__

2/3 of the achondroplastic offspring are heterozygous (the other 1/3 is homozygous).
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AlexxAlexx
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Taylor14 Author
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#4
10 years ago
That really helps me. Thanks Allexx and bio_man
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