3.4.3 - Crossing Over

Monday 19th February ‘24

What is it?

• Exchange of alleles between homologous chromosomes.

• Recombines alleles that wouldn’t normally be found on the same chromosome

• Inherited together in gametes - leads to increases in genetic variation.

• Random - likelihood of recombination taking place and the chances of a chiasma (point in which chromosomes break) forming can be increased/decreased, factors affecting this:

  • The distance of the loci on the chromosome

  • The distance to the centromere.

How do life-cycles change vary between organisms?

• Gamete formation usually occurs with meiosis.

• Process happens to form gametes just before an embryo stage.

• Some plants have alternating sexual and asexual generations in their lifecycle where haploid spores can be produced through meiosis and gametes through mitosis.