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KVPY Sample Paper KVPY Stream-SX Model Paper-16

  • question_answer
    Silky fur is a recessive trait in a breed of cats. An amateur breeder has procured a stock of 1000 cats of which 160 are silky-furred. As he is away, his wife happily sells all these 160 cats for a handsome price. On his return, the husband is upset and has no option but to breed the remaining stock. What percentage of the next generation will be silky-furred?

    A) \[16%~\]

    B) \[8%\]

    C) \[4%\]

    D) \[2%\]

    Correct Answer: B

    Solution :

    Frequency of individuals having silky fur \[\left( {{q}^{2}} \right)=0.16\]
    Frequency of allele for silky fur \[(q)=\sqrt{0.16}=0.4\] Frequency of allele for dominant allele (\[p\]) =\[~1-0.4=0.6\]
    Frequency of individuals having dominant allele \[\left( {{p}^{2}} \right)=0.36\]
    Number of individuals with dominant alleles in a population of 1000 cats =360
    Frequency of individuals with heterozygous individuals \[\left( 2pq \right)=2\times 0.4\times 0.6=0.48\]
    Number of individuals with heterozygous individuals in a population of 1000 cats =480
    Total number of individuals with dominant allele \[=360+360+480=1200\]
    Total number of individuals with recessive allele = 480
    Frequency of individuals with recessive\[=\frac{480}{1680}=0.285\]
    Frequency of individuals with recessive alleles \[=0.285\times 0.285=0.0812\approx 8%\]


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