what happens during crossing over

Crossing over is the exchange of DNA segments between homologous chromosomes during meiosis, usually in prophase I. This creates new combinations of genes in the resulting egg or sperm cells, which increases genetic variation.

What happens

• Homologous chromosomes pair up.
• Non-sister chromatids break and rejoin at points called chiasmata.
• Small DNA segments are swapped between the chromosomes.
• The new chromatids carry mixed genetic information.

Why it matters

• It helps produce genetically unique offspring.
• It increases variation in a species.
• It is one reason siblings can look similar but not identical.

Simple example

If one chromosome has one version of a gene and its partner has a different version, crossing over can shuffle those versions so the gametes end up with new gene combinations.

TL;DR: Crossing over is a DNA swap between paired chromosomes during meiosis that boosts genetic diversity.