1. Meiosis
Meiosis: Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
Two distinct divisions: Meiosis I and Meiosis II
Meiosis is the formation of human sex cells: sperm and egg

2. Chromosome Number Each individual has sets of chromosomes
Homologous: term used to refer to chromosomes that each have a corresponding chromosome from the opposite-sex partner
A cell that contains both sets of homologous chromosomes is said to be diploid, which means “two sets
Represented by 2N
Have two homologues of each chromosome
Has chromosomes found in pairs

3. Chromosome Number
Haploid: term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes
Represented by N
Egg and Sperm=Haploid Cells
Fertilized Egg=Diploid Cell

4. Meiosis I Cells begin to divide in a way that looks similar to mitosis
Differences between Meiosis and Mitosis:
In prophase of Meiosis I, each chromosome pairs with its corresponding homologous chromosome to form a structure called a tetrad
4 chromatids in a tetrad
As homologous chromosomes pair up and form tetrads in meiosis I, they exchange portions of their chromatids in a process called crossing-over
Exchange of alleles from new genes

5. Meiosis I Differences between Meiosis and Mitosis:
During anaphase I, chromatids do not separate at the centromere and pull the homologous chromosomes toward the ends of the cell

6. Meiosis II
Two cells produced in Meiosis I now enter a second meiotic division
No interphase in second meiotic division (no DNA replication)
Paired chromatids separate in this second division in anaphase II
Result: Four daughter cells containing just 2 chromosomes each and are haploid (N)

8. Human Genes 23 Pairs of chromosomes
44 Autosomes
Autosome is a chromosome that is not a sex chromosome
2 Sex Chromosomes
Can see the process of mitosis and meiosis along with the 23 pairs of chromosomes by examining a karyotype
Photograph of chromosomes grouped in order in pairs

9. Comparing Mitosis and Meiosis
Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells