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rl127 rl127
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11 years ago
I just cannot grasp this section...any help would be much appreciated!

1.  Which type of allele can be passed down from phenotypically normal parents?

2.  What is the probability of a person having sickle cell disease if one parent has the disease and the other is homozygous normal?

3.  What is the probability of a person having Huntington's disease if one parent is affected and the other is homozygous normal?
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wrote...
#1
11 years ago
1. recessive?
wrote...
#2
11 years ago
1 Recessive
2. 0% if female, 50% if male
3. i belive same as #2
wrote...
#3
11 years ago
1.) If parents are heterozygous (and as a result phenotypically normal), then they can pass their recessive allele which codes for the disease.

2.) 0% (all offsprings will be heterozygous)

3.) 0% (again)

actually i don't know if these two are sex-linked or not, so im sorry if I'm wrong.
wrote...
#4
11 years ago
1. Any allele.
2. 50-50
3. I think Huntington's is autosomal dominant. If that is correct, the odds are 100%.
wrote...
#5
11 years ago
for number 3, it depends if the person with huntingtons is homozygous or hetero because its dominant.
these are the two cases:
affected parent: HH
normal : hh
child= 100% chance

affected parent: Hh
normal: hh
Child= 50% chance
your teacher is probably going for the second scenario, since the chances of two grandparents with huntingtons mating to produce the HH isnt all that likely.
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