Download Mitosis vs Meiosis

Meiosis
• First nuclear division
– 46 X’s split into 2 nuclei with 23 X’s (one of
each kind of chromosome)
• Second nuclear division
– 23 X’s split into 2 nuclei with 23 single copy
chromosomes
• Cytokinesis follows both divisions, but
interphase only follows second division.
Meiosis
(Prophase I)
• Process: synapsis
• Two pairs of
homologous = tetrad
• Trading chromosome
pieces is crossing over.
• The X formed by “legs”
of the chromsomes
overlapping is called a
chiasma
Where
• Mitosis: Any cell not in G0 phase, except
in the gonads (ovaries and testes)
• Meiosis: In the gonads, the germ cells
give rise to the gametes (egg and sperm)
When
• Mitosis: throughout life in some cells, but
cell division stops in nerve cells and
muscle cells early in life (2-3 years old).
• Meiosis:
– Females: Begins before two years old, then
starts again during puberty with one egg
made each month. Menopause is when eggs
are no longer formed.
– Males: Happens throughout life from puberty
to death.
Result
• Mitosis: 2 Diploid cells with 46 single copy
chromosomes.
• Meiosis: 4 haploid cells with 23 single
copy chromosomes (one of each kind)
– Males: All four are viable cells (sperm)
– Females: Of the four cells created, only one
will become an egg and the other three
becoming polar bodies with little cytoplasm,
yet having the full 23 chromosomes.