GATE 2024 BT Q.16: solution and answer

Official answer: BSource: Official answer key, GATE 2024 BT (IISc Bengaluru)

1. The law of segregation states that the two alleles at a single gene locus (present on homologous chromosomes) separate from each other during meiosis I, so each gamete formed receives only one of the two alleles.

2. Option (A) mitochondrial genes: mitochondrial DNA is inherited maternally and cytoplasmically, following extranuclear inheritance rules, not Mendelian nuclear segregation — incorrect.

3. Option (B) alleles of a gene: these are the two alternative forms of one gene at one locus on a pair of homologous chromosomes; their separation during anaphase I of meiosis is exactly what the law of segregation describes — correct.

4. Option (C) linked genes on the same chromosome: this describes a multi-locus relationship (linkage and recombination frequency), a separate concept from the single-locus segregation of alleles — incorrect.

5. Option (D) unlinked genes on the same chromosome: genes located on the same chromosome are, by definition, linked, so this description is internally inconsistent; more importantly, it concerns the relationship between multiple loci (the domain of independent assortment), not the segregation of one gene's two alleles — incorrect.

6. Therefore only option (B) correctly identifies what the law of segregation applies to.