the process of meiosis

blue eyes

Would someone be able to explain the process of meisois to me in a relatively simple way that I will be able to understand. Becasue i really dont understand it.
Thank-you heaps in advanced

LilMrsDahamsta

Wikipedia article on meiosis

Panserborn

Easiest way to simply explain meiosis is by putting it in context of general cell biology.

As mammals, we carry 2 copies of each chromosome in each somatic cell (i.e., doesn't include germ cells or mature red blood cells); this is called "diploid" and is represented by the notation "2N". In dividing cells, the cell cycle is divided into 4 main stages - G1 phase where the cell is pretty much just doing its thing, S Phase where the cell replicates all its nuclear DNA in preparation for cell division, G2 phase where, again, the cell is minding its own business, and finally M phase where the cell divides - AKA mitosis.

From the point of view of understanding meiosis, S phase is the important phase. Since we normally have 2 copies of each chromosome (2N), after S phase this will double (4N) as all the DNA is replicated - essentially giving the cell 4 copies of each chromosome. During normal cell division (mitosis), 2 copies of each are segregated into 2 daughter cells, bringing you back to square one - 2 cells, each with 2N amount of chromosomes.

However, meoisis is a special type of devision used to generate the germ (sperm and egg) cells and these require that only one copy of each chromosome is present (1N). The reason for this is that upon fertilisation, one egg (1N) and one sperm (1N) will fuse to generate the 2N embryo - the normal genetic complement of a normal cell. If the germ cells had 2N then the embryo will be 4N, and then 8N when it undergoes S-phase - this is bad and will usually abort if it happens by accident.

Therefore, meoisis is a process where a post S-phase cell (total 4N complement) will essentially undergo mitosis twice without a second S phase; resulting in 4 cells - each containing 1 copy of each chromosome.

It is a little bit more complicated than this (bits of chromosomes get switched around a bit to generate genetic diversity) but this is essentially the nuts and bolts of it. Post or PM me if you need clarification on any point.