Q.What is known as cytological isolation ?

Cytological isolation blocks gene flow between populations through incompatible chromosome structure or number, not through behavioural or geographic barriers.

When two diverging populations accumulate differences in chromosome number or structure (such as inversions, translocations, or a difference in ploidy), any hybrid formed by mating between them will have chromosomes that cannot pair up properly during meiosis; this faulty pairing disrupts normal gamete formation, making the hybrids sterile or so inviable that they fail to reproduce, which in turn prevents gene flow between the two populations even if they can still physically mate. This is classed as a post-mating (post-zygotic) isolating mechanism, distinguishing it from pre-mating barriers like habitat or behaviou …