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Meiosis
The formation of gametes (sex cells)
Some Vocab• Diploid (2n): two sets of chromosomes–You are diploid ( 46 chromosomes)•1 set from mom •1 set from dad
• Haploid (n): one set of chromosomes–Reproductive cells are haploid
(23 Chromosomes)• Eggs• Sperm
2n
n
Some Vocab• Homologous Chromosomes: two
chromosomes with the same gene sequence as another, one derived from each parent.
What is Meiosis?
Meiosis is a process of reduction division in which the number of
chromosomes per cell is cut in half.
What is Meiosis?Meiosis involves two divisions
◦Meiosis I◦Meiosis II
Meiosis IInterphase I – DNA replicatesProphase I – Crossing over occursMetaphase I – Chromosomes line upAnaphase I – Chromosomes are pulled
apartTelophase I/Cytokinesis – Nuclear
membranes forms. The cell separates into two cells.
What is Crossing Over?Crossing over is when two homologous
chromosomes pair up and exchange segments of their genetic material.
• Crossing over results in genetic recombination.
• Crossing over is what makes every egg and sperm cell unique.
• Crossing over is why you are not exactly like your siblings.
Crossing Over
Crossing Over
Crossing Over
Meiosis I
Meiosis I
Meiosis I
Meiosis I
Meiosis I
Meiosis IIVery similar to mitosis
FINAL PRODUCT = 4
HAPLOID DAUGHTER
CELLS
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II
Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II
Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II
Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II
Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Meiosis II
Gamete FormationMales
• In male animals, the haploid gametes produced in meiosis are called sperm.
Females• In female animals,
one cell receives most of the cytoplasm and will become an egg cell. The other three cells produced are known as polar bodies and do not participate in reproduction.
Gamete FormationMales
SpermatogenesisFemalesOogenesis
Meiosis MitosisPurpose
# of divisions required
# of cells needed to begin
# of daughter cells produced
# of chromosomes in daughter cells (n/2n)
# of chromosomes in daughter cells in
humans
Are the daughter cells identical to the parent
cell?Does crossing over
occur?
To produce gametes(sex / gametic cells)
Production of body cells
2 1
4 2
Half the number of the parent cell (n)
The same number as the parent cell (2n)
No
No
Yes
Yes
1 1
23 46
