Correct option is A
The correct answer is option (1): Translocation.
Explanation:
In translocation, a segment of one chromosome is transferred to another chromosome, and when homologous chromosomes pair during meiosis, a cruciform structure forms at the point of translocation. This happens because the chromosomes that have undergone translocation attempt to align their regions of homology during synapsis (the pairing of chromosomes in meiosis), and this alignment results in the characteristic "cross" shape. The cruciform structure is particularly visible during the prophase I stage of meiosis.
In the case of translocation, homologous chromosomes exchange genetic material, which leads to unusual alignment patterns, including the formation of a cross-shaped structure.
Information Booster:
Translocation and Cruciform Structure: Translocation occurs when a portion of one chromosome is moved to another, non-homologous chromosome. When the chromosomes align in meiosis, acruciform structure(cross shape) forms at the site of translocation. This structure arises because of the misalignment of regions that were not previously paired together, creating the cross-shaped configuration during synapsis.
Inversion: Inversion is a chromosomal rearrangement where a segment of a chromosome is flipped end to end. The chromosome forms a loop to pair up during meiosis, but it does not form a cross-shaped cruciform structure.
Why the other options are incorrect:
Option (2): Inversion: In inversion, a segment of a chromosome is reversed end to end. During meiosis, this leads to the formation of a loop structure, not a cruciform structure. The chromosome aligns with its homologous partner, but because part of it is reversed, it forms a loop rather than a cross.
Option (3): Deletion: In deletion, a segment of the chromosome is missing. This typically results in the chromosome being shorter and does not form a cruciform structure during meiosis.
Option (4): Duplication: In duplication, a segment of the chromosome is repeated. While this results in a larger chromosomal segment, it does not lead to the formation of a cruciform structure. Instead, it leads to extra copies of the duplicated segment.
