What percentage of the offspring is predicted to be carriers but not manifest the disease?

Question

What percentage of the offspring is predicted to be carriers but not manifest the disease??  
A. 0%  
B. 25%  
C. 50%  
D. 100%

Accepted Answer

Correct Answer: (C)50%. 
Rationale: Fifty percent of the offspring will be carriers who do not manifest the disease.When two heterozygous parents carry a recessive disease allele, classic Mendelian inheritance predicts a 1:2:1 genotypic ratio. This means some children will be unaffected non-carriers, some will be unaffected carriers, and some will express the disease.A) 0%A value of 0 percent would indicate that none of the offspring inherit the recessive allele.However, when both parents are carriers (Cc), each parent contributes either a dominant (C) or recessive (c) allele. This guarantees that some children will inherit at least one recessive allele.Therefore, it is genetically impossible for 0% of the offspring to be carriers in this scenario, making this option incorrect.B) 25%Twenty-five percent represents the proportion of offspring who inherit two recessive alleles (cc).These individuals would manifest the disease because they lack a normal dominant allele. This group is affected, not merely carriers.Since the question asks for carriers who do not show symptoms, this option is incorrect.C) 50%A Punnett square for Cc × Cc produces the following outcomes:25% CC → unaffected, not carriers50% Cc → unaffected carriers25% cc → affectedIndividuals with genotype Cc carry one copy of the disease allele but do not express the disorder because the dominant allele masks it.Thus, half of all offspring are expected to be carriers without manifesting the disease, making this option correct.D) 100%One hundred percent would mean that every child inherits exactly one recessive allele.This outcome would only occur if one parent were homozygous recessive (cc) and the other homozygous dominant (CC), not when both parents are heterozygous.With two carrier parents, offspring can be CC, Cc, or cc, so 100% carriers is not possible.This option is incorrect.Conclusion:When both parents are heterozygous carriers of a recessive disease, the expected distribution of offspring is:25% unaffected non-carriers (CC)50% unaffected carriers (Cc)25% affected (cc)Therefore, the percentage of offspring who are carriers but do not manifest the disease is 50%.

What percentage of the offspring is predicted to be carriers but not manifest the disease?

A
0%

B
25%

C
50%

D
100%

Fifty percent of the offspring will be carriers who do not manifest the disease.

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What percentage of the offspring is predicted to be carriers but not manifest the disease?

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

Fifty percent of the offspring will be carriers who do not manifest the disease.

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Related Questions

A
0%

B
25%

C
50%

D
100%