Meiosis: Creation of Meiosis: Creation of the Sex Cellsthe Sex Cells

What What is is Meiosis??Meiosis?? MeiosisMeiosis- creation of sex cells (eggs, - creation of sex cells (eggs,

sperm)sperm) Occurs in testes in males, ovaries in Occurs in testes in males, ovaries in

femalesfemales At the end, 4 cells are created that At the end, 4 cells are created that

are NOT identical to the starting cell. are NOT identical to the starting cell.

Karyotypes Karyotypes Display of the 46 chromosomes of an Display of the 46 chromosomes of an

individualindividual 23 23 homologous pairshomologous pairs of of

chromosomeschromosomes

Female Male

Homologous ChromosomesHomologous Chromosomes Two chromosomes of each matching Two chromosomes of each matching

pairpair– 1 from mom & 1 from dad1 from mom & 1 from dad

Diploid/ HaploidDiploid/ Haploid Diploid (2n)-Diploid (2n)- cells with 2 homologous cells with 2 homologous

sets of chromosomes (2n= 46 in sets of chromosomes (2n= 46 in humans)humans)

Haploid (n)-Haploid (n)- Single set of Single set of chromosomes (n= 23 in humans)chromosomes (n= 23 in humans)– Sex cells produced through meiosisSex cells produced through meiosis

Human Life CycleHuman Life Cycle

Mitosis vs. MeiosisMitosis vs. Meiosis MITOSISMITOSIS MEIOSISMEIOSIS

– Body cellsBody cells - Gametes- Gametes– Produces 2 identicalProduces 2 identical - Produces 4 - Produces 4

different cells (diploid)different cells (diploid) cells cells (haploid) (haploid)

MeiosisMeiosis 2 parts- Meiosis I and Meiosis II2 parts- Meiosis I and Meiosis II

VideoVideo MeiosisMeiosis

Crossing OverCrossing Over Human offspring are genetically Human offspring are genetically

different from their parents…different from their parents… WHY??WHY?? Occurs during Occurs during Prophase IProphase I Homologous chromosomes exchange Homologous chromosomes exchange

some genetic materialsome genetic material Why is this important??Why is this important??

– Allows for more variation in the cells. Allows for more variation in the cells.

Crossing OverCrossing Over

Mitosis vs. MeiosisMitosis vs. Meiosis

Mitosis vs. MeiosisMitosis vs. Meiosis Describe two differences between Describe two differences between

meiosis and mitosis.meiosis and mitosis.– 1) 1) – 2) 2)

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