The interchange of segments between non-homologous chromosomes is known as:

Question

Accepted Answer

The correct option is 2: Translocation

Translocation is the precise term in genetics and molecular biology for the chromosomal aberration described: the interchange of segments between non-homologous chromosomes. Chromosomes are considered non-homologous when they do not belong to the same pair, meaning they carry genes for different traits. This genetic event occurs when a segment of one chromosome breaks off and attaches itself to an entirely different, non-paired chromosome. When the exchange is mutual—meaning segments are swapped between the two non-homologous chromosomes—it is called a reciprocal translocation. This is a significant mutation because it can change the physical location of a gene, potentially placing it under the regulatory control of a different set of genes, which can lead to diseases like certain types of leukaemia or cause fertility issues.

The incorrect option is 1: Crossing over

Crossing over is a fundamental biological process of genetic recombination that occurs only between **homologous chromosomes**, specifically between non-sister chromatids, during Prophase I of meiosis. The purpose of crossing over is to exchange corresponding segments of genetic material, thereby shuffling alleles and increasing genetic diversity in the gametes. This is a carefully regulated, normal event, distinct from the mutational nature of a translocation. Since the question specifies the interchange between **non-homologous** chromosomes, crossing over is fundamentally incorrect.

The incorrect option is 3: Inversion

Inversion is a type of structural chromosomal mutation where a segment of a chromosome breaks off, flips around, and reinserts itself into the same chromosome, but in the reverse orientation. Therefore, the gene sequence is reversed within the chromosome. Critically, inversion involves changes **within a single chromosome** and does not involve the interchange of segments with any other chromosome, whether homologous or non-homologous. Its primary effect is the internal rearrangement of gene order on one chromosome arm.

The incorrect option is 4: Duplication

Duplication is a chromosomal abnormality that results in the repetition of a section of a chromosome, leading to extra copies of the genes located in that segment. This mutation increases the total amount of genetic material in the cell, leading to an increase in gene dosage. Duplication typically arises from unequal crossing over or errors in DNA replication, and like inversion, it is an event that occurs **within a single chromosome or homologous pair**. It is a change in gene quantity, not an interchange between two separate, non-homologous chromosomes.