Huntington’s disease is carried on the dominant allele. In a situation where twoheterozygous parents have the disease, what percentage of their offspring arepredicted to be disease-free?

Question

Huntington’s disease is carried on the dominant allele. In a situation where twoheterozygous parents have the disease, what percentage of their offspring arepredicted to be disease-free??  
A. 0%  
B. 25%  
C. 50%  
D. 100%

Accepted Answer

Correct Answer: (B)25%. 
Rationale: 25% of the offspring are predicted to be disease-free.Huntington’s disease is caused by a dominant allele. This means that a person only needs one copy of the disease allele to show the condition. Individuals with genotypes HH or Hh will have Huntington’s disease, while only individuals with genotype hh (homozygous recessive) will be disease-free.In this question, both parents are heterozygous (Hh), meaning each parent has one dominant disease allele and one normal recessive allele.When these parents reproduce, their possible genetic combinations can be shown using a Punnett square:H × H → HH (affected)H × h → Hh (affected)h × H → Hh (affected)h × h → hh (disease-free)This gives the following proportions:25% HH → affected50% Hh → affected25% hh → disease-freeOnly the hh offspring do not have the disease.A) 0%Two heterozygous parents can produce homozygous recessive offspring (hh), which are disease-free. Therefore, the percentage cannot be zero.B) 25%One out of four possible offspring genotypes (hh) does not carry the dominant disease allele. That corresponds to 25% of the offspring being disease-free.C) 50%Fifty percent represents the heterozygous offspring (Hh), but these individuals still have the disease because the allele is dominant.D) 100%Not all offspring will inherit the dominant allele. There is always a chance of producing hh offspring from two heterozygous parents.ConclusionWhen two heterozygous parents with a dominant disorder have children, only the homozygous recessive offspring will be disease-free. This occurs in 25% of cases. Therefore, the correct answer is B) 25%.

Huntington’s disease is carried on the dominant allele. In a situation where twoheterozygous parents have the disease, what percentage of their offspring arepredicted to be disease-free?

A
0%

B
25%

C
50%

D
100%

25% of the offspring are predicted to be disease-free.

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Huntington’s disease is carried on the dominant allele. In a situation where twoheterozygous parents have the disease, what percentage of their offspring arepredicted to be disease-free?

A 0% B 25% C 50% D 100%

25% of the offspring are predicted to be disease-free.

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Related Questions

A
0%

B
25%

C
50%

D
100%