VERY GOOD YOUTUBE VIDEO: https://youtu.be/8yyxn0ERtBg
Meiosis is the splitting of sex cells during sexual reproduction to pass on 23 chromosomes to the offspring.
MEIOSIS IS MITOSIS BUT FOR SEX CELLS (GAMETES)
Results in 4 daughter cells that are haploid and have novel chromatids due to crossing over.
Long explanation: One full diploid sex cell from each parent (one sperm, one egg) splits twice creating 4
new cells called daughter cells. This is done in three phases: interphase, meiosis one, and meiosis two.
In interphase, a diploid sex cell will double its chromosomes from 46 to 92 in one cell. These new (novel) chromosomes are still the same as before just twice the number (homologous).
In meiosis one, the cell with 92 chromosomes will split into two diploid daughter cells with non-homologous chromosomes.
In meiosis two, the two diploid daughter cells will split again ending the entire cycle by creating 4 non-homologous haploid daughter cells ready to be merged with another haploid cell of a sperm or egg to create a diploid zygote.
The Three Methods for Genetic Variation
Independent Assortment - genes that do not reside on the same chromosome may sort independently (anaphase 1 of meiosis)
the formula for possible combinations is 2^n, where n = # of haploid chromosomes
Random Fertilization - only one sperm will fertilze the egg and turn the haploid into a diploid. It’s random which sperm will get there.
fertilization is the opposite process of meiosis
Crossing Over - genetic information may be exchanged between homologues, further shuffling the genetic information of the eventual gamete (prophase 1)
uses non-sister chromatids
These three process are found in all eukaryotes!