Science Word Wednesday: Chromosomal Crossover

Sep 23, 2020
By Mohamed Nasr

Chromosomal Crossover

(noun. /kro-mo-SO-muhl KROSS-over/) 

What does it mean? 

Chromosomal crossover, also known as “crossing over”, is the process of chromosomes aligning and exchanging portions of their genetic material. The areas in the chromosome that cross over are called chiasmata. This crossover occurs during gamete formation in the prophase of meiosis I.

This figure depicts the process of crossing over and how this process results in recombinant chromosomes that contribute to genetic diversity. This figure was created with

How do I use it in a sentence?

Crossing over contributes to genetic diversity by producing chromosomes with mixed paternal and maternal genetic materials”

History of usage

Thomas Hunt Morgan was the first to describe “crossing over” as a theory in 1912, and it was Barbara McClintock who validated this theory in 1931. 


Related terms

Holliday Junction


Genetic recombination



Fields of study in which this word is commonly used


Edited by Emma Goldberg and Anna Wheless