With the help of given pedigree, find out the probability for the birth of a child having no disease

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Question

With the help of given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in F3 generation.

Accepted Answer

Correct Answer: B — 1/4Step-by-step Solution:From the pedigree, the disorder follows X-linked recessive inheritance. Using Xc for the disease allele and XC for the normal allele:F1 cross: Carrier female (XCXc) × Normal male (XCY). This could produce an affected male (XcY) in F2.F2 cross (consanguineous mating described in pedigree): Carrier female (XCXc) × Affected male (XcY). Offspring possibilities:XCXc — carrier female (unaffected carrier) → probability 1/4XcXc — affected female → probability 1/4XCY — normal male → probability 1/4XcY — affected male → probability 1/4The question asks for probability of a child who is unaffected (no disease) AND a carrier (has mutation in one allele). Only XCXc females satisfy both conditions: they carry one disease allele (Xc) but are phenotypically unaffected (because XC is dominant). Probability = 1/4.Extended Explanation:In X-linked recessive inheritance: Males are either affected (XcY) or normal (XCY) — they cannot be carriers (they only have one X chromosome). Females can be: normal (XCXC), carrier (XCXc), or affected (XcXc). Classic examples of X-linked recessive disorders: Haemophilia A (factor VIII deficiency), Haemophilia B (factor IX), Duchenne Muscular Dystrophy (DMD), Colour blindness (red-green), G6PD deficiency. In pedigree analysis, X-linked recessive traits show: more affected males than females; affected males get the allele from carrier mothers; father cannot pass the allele to sons (but passes to all daughters).Key Concepts: Pedigree analysis, X-linked recessive inheritance, carrier females, probability calculation, sex-linked disorders.

With the help of given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in F3 generation.

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With the help of given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in F3 generation.

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