– If both parents replicated cells using mitosis,
a child would receive 46 chromosomes from
dad & 46 from mom given a grand total of…?
– 92! (Way too many)
– So…if dad could give 23 + 23 from mom =
46! (Bingo!)

Binary Fission

Budding

Fragmentation
Better when the
environment is not
favorable or
becomes unstable
Meiosis
Meiosis
• Def: 2 successive cell divisions that produce
gametes
• What does that mean?
– Successive  one right after the other
– Gametes  a haploid reproductive cell, either an
egg or a sperm
– Haploid  containing only 1 of every
chromosomes (n)
– Diploid  containing 2 of every chromosome (2n)
Some More Vocabulary
• Body Cells
– AKA  somatic cells
– Ex  skins cells, nerve cells, blood cells
– Diploid  46 chromosomes (23 pairs)
• Sex Cells
– AKA  germ cells
– Ex  egg & sperm
– Haploid  23 chromosomes (all single)
Q: A mutation in which type of cell would be worse?
Chromosome
Number in
Mitosis
Meiosis = 2 Mitosis
P1M1A1T1  P2M2A2T2
With a few slight differences!
Meiosis = 1st Division
Prophase I
Prophase 1  Crossing Over
Metaphase I
Metaphase 1  chromosomes
line up randomly 2 by 2
forming a tetrad (4 across)
Anaphase 1  homologous
chromosomes are pulled to
opposite poles (sister
chromatids do not separate!)
Anaphase I
Telophase I
Crossing Over
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
Single
Chromosomes line Sister Chromatids
are pulled apart
up
Meiosis II
2nd Division
Cells divide twice! (Mitosis divide only once)
 End result is 4 different cells instead of 2
genetically identical cells!
 Chromosome number is cut in half!

› 2n (diploid)  n (haploid) = Meiosis
› 2n  2n = Mitosis

Crossing Over!
• The purpose of meiosis is…?
• To produce gametes which are necessary for
sexual reproduction.
• Allows for new mixtures of combinations 
called genetic recombination
• VARIATION!