** Mitosis is asexual reproduction & occurs ONLY in regular old body cells called SOMATIC CELLS (skin, nails, your pancreas, etc..) NOT sperm and eggs 
** Produces two identical diploid (2n) cells

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We call somatic cells diploid (2n) meaning you have
2 copies of each chromosome (1/2 from mom and ½ from dad)
Autosomal chromosomes are non-sex chromosomes
› These contain genes that have nothing to do with determining your sex
Each of your cells contain 44 autosomal chromosomes and 2 sex chromosomes (XX for female and XY for male) for a total of 46 chromosomes in each nuclei of your cells

Replicates
Above are Homologous
Chromosomes - Same chromosome with same types of genes on each chromosome, just different variations from each parent

FROM MOM
FROM DAD

**Required for Sexual Reproduction
**Diploid cells divide twice to produce haploid (n) sperm or egg (each have 23 chromosomes)
**Produced in the ovaries (females) and testes
(male)
**Results in 4 NON-IDENTICAL haploid (n) cells
 Genetic recombination creates genetic variability in either sperm or egg
 For each meiotic division, 4 sperm are produced but typically only 1 egg survives

**After interphase (DNA replication phase)
**Meiosis I  Prophase I, Metaphase I,
Anaphase I, telophase I
**Meiosis II  Prophase II, Metaphase II,
Anaphase II, Telophase II and cytokinesis
**4 cells, the gametes!!

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Although numerous sperm attempt to fertilize the egg, only one will succeed
Diploid zygote – will undergo mitosis

Male = XY Female = XX

Meiosis occurs in 2 phases. Meiosis 1 and
Meiosis 2 with cytokinesis following. The process results in 4 non-identical haploid cells
After Meiosis 1
From your From your
Dad Mom
Replication
Homologous chromosomes –
SAME chromosome type (have the same types of genes)
A tetrad is formed
Crossing Over between nonsister chromatids
During
Prophase 1 of
Meiosis 1 –
Results in genetic recombination

** A reassortment of chromosomes and genetic information they carry
**crossing over between non-sister chromatids during Prophase 1
**independent assortment of homologous chromosomes

**Pink is from your mom, blue from your dad
**Non-sister chromatids exchange genetic information

Independent Assortment leads to genetic variability- homologous chromosomes are sorted before shipment to gametes independently of how the other pairs were sorted

**chromosomes of a homologous pair (tetrad) fail to separate and move to the same pole of the cell. Some gametes may have an extra chromosome while others lacking
** Down syndrome occurs because of this. Called trisomy 21, there are 3 of chromosome #21 rather than a pair!

Male with no chromosomal abnormalities

Trisomy 18 – Due to Non-disjunction

Mitosis
• Occurs in 1 stage •
Meiosis
Occurs in 2 stages
• Produces 2 genetically identical diploid cells
• Produces 4 genetically different haploid cells (genetic recombination)
•
• It is Asexual Reproduction
Occurs in body cells (autosomal) and creates two diploid cells
• For Sexual Reproduction
• Produces “clones” with no genetic variability
• Produces genetically variability due to recombination
• Occurs in sex cells called gametes or germ cells and four haploid cells
(sperm and egg)
• 2n=46  22 pair of autosomal chromosomes and 1 pair sex chromosomes
• n=23  22 autosomal chromosomes and 1 sex chromosome
• Forms a tetrad

Meiosis Mitosis