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    ​The pedigree given below represents the genotype at four different loci the children in generationIII.​​Which one of the given genotypes is likely to
    Question

    The pedigree given below represents the genotype at four different loci the children in generationIII.

    Which one of the given genotypes is likely to represent the genotype of individual II-1?

    A.

    B.

    C.

    D.

    Correct option is C

    Explanation-

    Given - The genotypes of the four children in generation III. Each child receives one allele from each parent at every locus. 
    Locus A:
    Children’s alleles:
                       III-1: A¹ A²
                       III-2: A¹ A²
                       III-3: A¹ A¹
                       III-4: A¹ A²
    From these:    A¹ and A² both appear among offspring. III-3 is A¹ A¹, meaning both alleles came from each parent => both parents must carry A¹. Since A² also appears, one of the parents must also carry A².
    So, II-1’s genotype at locus A = A¹ A²
    Locus B:
    Children’s alleles:
                       III-1: B¹ B²
                       III-2: B¹ B²
                      III-3: B¹ B¹
                      III-4: B² B²
    This means - Parent II-1 must carry B¹ (for III-1, III-2, III-3) and must also carry B² (for III-1, III-2, III-4).
    So, II-1’s genotype at locus B = B¹ B²
    Locus C:
    Children’s alleles:
                      III-1: C¹ C²
                      III-2: C² C²
                      III-3: C¹ C²
                      III-4: C¹ C¹
    This suggests - C¹ C², C² C², and C¹ C¹ offspring observed → all combinations. Only way this is possible: II-1 is C¹ C²
    So, II-1’s genotype at locus C = C¹ C²
    Locus D:
    Children’s alleles:
                     III-1: D¹ D²
                     III-2: D¹ D²
                     III-3: D¹ D²
                     III-4: D¹ D¹
     Everyone gets D¹, some get D². Thus one parent is D¹ D¹ (always provides D¹). The other must be D¹ D²
    Since III-4 is D¹ D¹, both alleles must be D¹ → one parent is D¹ D¹. Since others have D², the other parent is D¹ D²
    Therefore, II-1 = D¹ D²

     Final Genotype of II-1:
    A¹ A², B¹ B², C¹ C², D¹ D² → This matches Option c

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