Meiosis produces genetic variation through:

1. Segregation

2. Independent Assortment

3. Crossing over (recombination)

All 3 randomly shuffle the alleles of the chromosomes in a parent cell into four different gamete cells -> meiosis produces different combinations of alleles = why children don’t look exactly like half the characteristics of each parents why siblings don’t look alike.

Segregation – the two alleles of a pair of homologous chromosomes separate into different cells during meiosis.

· In the first division, Meiosis I, chromosomes line up in homologous pairs at the cwell equator (with each member of a homologous pair opposite the other on either side of the equator)

· Therefore, when each member of the homologous pair is pulled to opposite poles by spindle fibres the two alleles for a gene are separated into different cells.

So, segregation means:

· You can end up with gametes with different alleles for a gene

· Either one of the alleles can then be passed on into the gene pool through a gamete

· This gives the opportunity for there to be different combinations of alleles from the parent when it fuses with another gamete to form a zygote (thereby increasing genetic variation from the parent)

Independent Assortment

· During Meiosis I, each homologous chromosome pair lines up and separates independently of how the other pairs line up.

· Each time a cell divides, the orientation of each pair will be different, producing different allele combinations each time. It shuffles alleles into a huge variety of new combinations.

Crossing Over - an exchange of sections of non sister chromatids between homologous chromosomes (shuffles alleles between homologous chromosomes

When the homologous chromosomes pair up and form tetrads, sections of the non sister chromatids can cross over at a point called a chiasma
A chiasma is the point where the two non sister chromatids cross over and exchange genetic material
The crossed sections can break and recombine at the chiasma resulting in chromosomes in the gametes with different allele combinations from those of the parent, therefore increasing genetic variation.

	Creado por carlacamilleri hace más de 10 años

(Genetic Variation ) Biology Apunte sobre Meiosis Producing Genetic Variation , creado por carlacamilleri el 18/06/2014.