Variability in sexual reproduction

[tiffne11294]

I'm studying for an exam and I've just made some "notes". Can someone just read through this and check if anything is wrong. Feel free to correct anything. Thanks. (sorry for the trouble)

Segregation:
>One chromosome from each homologous pair is selected at random to form each gamete.
>The separation of chromatids produces gametes which are different from each other (have different allele combinations) as well as having different genetic information from the parents. All gametes are different to the parent cell and are not identical to each other.

Independent Assortment:
>When the homologous chromosomes line up during meiosis, it is random as to which way they line up. Alleles on one pair of homologous chromosomes separate independently from allele pairs on other chromosomes.
>Different pairs of genes are passed to offspring independently so that new combinations of genes, present in neither parent are possible. This allows for variation in the alleles of the newly formed gametes and assists genetic variability. This allows survival of organisms in a changing environment, leading to an increased chance of population survival.

Crossing Over:
>Homologous pairs of chromosomes line up during meiosis. Chromatids from each chromosome cross-over each other (entangle). At the point(s) they cross/chiasma(ta), the chromatids exchange material and then separate to form new chromatid combinations.
>This leads to the recombining of genetic material of the two parents so alleles are exchanged and making all the gametes unique/different. This new chromosome is unique and produces a new genetic combination which increases genetic variability. This allows survival of organisms in a changing environment, leading to an increased chance of population survival.

Fertilisation:
>This results in variation of genetic material by bringing together one male and one female gamete each containing different genetic information from the parents. Fertilisation produces new combinations of alleles (genetic variation).
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>All these processes lead to genetic variation through existing genes producing new combinations of alleles and makes all gametes unique/different.