Genetic diversity during meiosis

Crossing over: Starts to occur during prophase 1. Homologous chromosomes form bivalents, as the chromosome arms become tangled when moving through cytoplasm. Crossing over occurs - the exchange of alleles between homologous chromosomes, leading to increased genetic variation. During anaphase 1, when the homologous chromosomes are pulled to opposite poles of the cell, the sections of entangled DNA break off and rejoin, forming recombinant chromatids. The point where the chromatids break and rejoin is called the chiasmata. Sister chromatids no longer identical.

Independent assortment: Occurs during metaphase 1 and metaphase 2. Orientation of homologous chromosome pairs during metaphase 1 and chromatids during metaphase 2 is random and independent of other pairs (maternal/paternal chromosomes can face either pole). Therefore, there are many different allele combinations that can form, leading to increased genetic variation.

DNA mutations: Mutations in the DNA that occurred during the S phase when DNA was replicated that was not found at the checkpoints also increases the genetic variation.

Random fertilisation: A large number of gametes are produced, and they fertilise randomly, so a large combination of alleles that could fuse to form offspring, therefore increasing genetic diversity.