Q.Mendel's Law of independent assortment holds good for genes situated on the:

Mendel's Law of Independent Assortment states that alleles of different genes segregate independently during gamete formation. This law works perfectly when genes are located on non-homologous chromosomes because such chromosomes assort independently during meiosis I—each pair moves to opposite poles without influencing the behavior of other pairs.

When genes sit on the same chromosome (linked genes), they tend to be inherited together and do not assort independently unless crossing over separates them. Homologous chromosomes carry alleles of the same genes at corresponding loci, so the question of independent assortment between different genes arises only when comparing genes on different chromosome pairs. Extra-nuclear genetic elements like mitochondrial or chloroplast DNA follow maternal inheritance patterns, not Mendelian laws. …

When Mendel crossed pea plants differing in two traits—say, seed shape and seed color—he observed something remarkable in the F₂ generation. The traits didn't travel together as a package. Instead, they assorted independently, producing a 9:3:3:1 ratio. Round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds all appeared in predictable proportions. This led him to propose the Law of Independent Assortment: during gamete formation, the segregation of alleles for one gene occurs independently of the segregation of alleles for another gene.

But here's the crucial question: under what physical conditions does this law actually hold true?

The answer lies in chromosome behavior during meiosis. Genes are carried on chromosomes, and during meiosis I, homologous chromosome pairs line up at the cell's equator. The key is that non-homologous chromosomes—chromosomes that are not partners in a pair—orient themselves randomly with respect to one another. One homologous pair's alignment doesn't influence how another pair lines up. When the cell divides, maternal and paternal chromosomes from different pairs assort into gametes in all possible combinations.

If two genes sit on different, non-homologous chromosomes, they behave exactly as Mendel described. Gene A on chromosome 7 and gene B on chromosome 9, for instance, will segregate independently because their chromosomes move to gametes without any physical connection or influence on each other.

Picture metaphase I directly rather than starting from the definition: homologous pairs line up at the equator, and each pair orients itself independently of every other pair (like several separate coin flips happening in the same room). Two genes assort independently only if …