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    ​In 1990, Bhattacharya et al identified that the wrinkled seed character of pea as described by Mendel is caused by a transposon-like insertion in a g
    Question

    In 1990, Bhattacharya et al identified that the wrinkled seed character of pea as described by Mendel is caused by a transposon-like insertion in a gene encoding Starch Branching Enzyme (encoded by the R allele). This leads to an RFLP pattern, when genomic DNA of round and wrinkled seed is digested with EcoRI and probed with the cDNA of the R gene product. The following is a representation of the hybridization pattern.

    Based on the above, which one of the following statements is INCORRECT?​​

    A.

    Lane 3 represents genomic DNA from plant with wrinkled seeds

    B.

    These DNA markers are co-dominant in nature

    C.

    Lane 1 represents genomic DNA from plant with round seeds

    D.

    If genomic DNA from F₂ progeny as obtained in Mendel’s work was analyzed by RFLP, the ratio of progeny with patterns in lane 1, 2, and 3 will be 2:1:1

    Correct option is A

    Explanation-

    RFLP is used here to distinguish alleles of the R gene (Starch Branching Enzyme).
    Round seeds: Functional R gene (no insertion).
    Wrinkled seeds: Transposon insertion disrupts R gene → larger DNA fragment due to insertion.
    Probe: cDNA of R gene → binds only to fragments containing the R gene or its disrupted version.
    Lane Analysis:
    From the gel image:
    Lane 1: One band (upper position) — longer fragment.
    Lane 2: Two bands — one at upper position (like lane 1), one at lower position (like lane 3).
    Lane 3: One band (lower position) — shorter fragment.
    Interpretation:
    Lane 1: Homozygous round (R/R) — no insertion → shorter fragment.
    Lane 3: Homozygous wrinkled (r/r) — insertion present → longer fragment.
    Lane 2: Heterozygous (R/r) — shows both bands.
    This implies:
    Lane 1 = Round (R/R)
    Lane 2 = Heterozygous (R/r)
    Lane 3 = Wrinkled (r/r)

    Analyzing each Option:
    Option a - Lane 3 represents genomic DNA from plant with wrinkled seeds.
    Lane 3 has the smaller fragment, hence round; this is the wrong statement. 
    Option b - These DNA markers are co-dominant in nature.
    Correct — both alleles visible in heterozygote (lane 2 shows both bands).
    Option c - Lane 1 represents genomic DNA from plant with round seeds.
    Correct — small fragment, no insertion, R/R.
    Option d - If genomic DNA from F₂ progeny (Mendel) was analyzed by RFLP, the ratio of patterns in lanes 1, 2, and 3 will be 1:2:1.
    Correct — classical Mendelian segregation.

    Final Answer: Option a is incorrect statement that makes it a correct answer.

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