- The following diagram shows meiotic pairing in an inversion heterozygote and a point where single crossing over has occurred
The resulting gametes produced may have
A. the chromosome having normal gene sequence
B. the chromosome having inverted gene sequence
C. a dicentricchromosome with duplication and deletion
D. an acentric chromosome having duplication and deletion
E. the chromosome having duplication and deletion
Which of the following combination will be most appropriate for the diagram shown:
(1) A, B, C and D (2) A, B and E
(3) B, C, D and E (4) A, C, D and E
Interpreting the diagram
The figure shows meiosis in an inversion heterozygote:
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One homolog has normal order A–B–C–D–E–F–G.
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The other has a paracentric inversion involving C–D–E–F (centromere outside inversion).
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Homologs form an inversion loop, and a single crossover occurs within this loop.
Standard consequences of a single crossover in a paracentric inversion:
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One chromatid remains normal in gene order.
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One chromatid remains inverted in the loop region.
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One recombinant chromatid is dicentric and carries a duplication and deletion.
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One recombinant chromatid is acentric and also carries a duplication and deletion.
Matching to statements A–E
A. Chromosome having normal gene sequence – produced (the non‑crossover normal chromatid).
B. Chromosome having inverted gene sequence – produced (the non‑crossover inverted chromatid).
C. Dicentric chromosome with duplication and deletion – produced as one of the crossover chromatids in a paracentric inversion loop.
D. Acentric chromosome having duplication and deletion – also produced as the other crossover chromatid.
E. Chromosome having duplication and deletion – this is true for both crossover chromatids, but it does not specify acentric/dicentric; since C and D already describe these more precisely, E is redundant in the context of “resulting gametes produced may have”.
The question asks which combination is most appropriate for the diagram shown; the classical four products of a single crossover in a paracentric inversion heterozygote are exactly A, B, C and D, corresponding to option (1).
