Meiosis
Chapter 11 Section 4
Chromosome Number
Nucleus contains
DNA
DNA contains genes
You get 1 side from
mom, one side from
dad. The genes
match up.
Diploid Cells
Diploid = 2 sets (di = 2), written 2N
Chromosomes that line up together are called
homologous chromosomes (homo = same)
line up together because they have the same
genes
Haploid = 1 set (half), written N
only 1 set of genes (sperm or egg cells)
Phases of Meiosis
Meiosis makes sperm
and egg cells, basically
the cell divides twice!
Meiosis 1 (PMAT 1)
Meiosis 2 (PMAT 2)
before meiosis starts
the chromosomes are
replicated
Human
Pea
Potato
Fruit Fly
Goldfish
Diploid
46
14
48
8
94
Haploid
23
7
24
4
47
Meiosis 1 - Prophase 1
Crossing over happens
during prophase 1
crossing over is when alleles
for the same genes are
exchanged
increases genetic diversity
Chromosomes form tetrads
when crossing over occurs
Meiosis 1
Metaphase 1 - tetrads line up in the middle of the cell
Anaphase 1 - homologous chromosomes separate
Telophase 1 and Cytokinesis - 2 new cells form
Meiosis 2
Prophase II - chromosomes become visible, nucleus goes
away
Metaphase II - chromosomes line up in middle of the cell
Anaphase II - sister chromatids separate
Telophase II and Cytokinesis - 4 new cells are formed
Gametes to Zygotes
Mitosis
Gametes - haploid or
sex cells that combine to
make a new individual
(a.k.a. sperm/egg cells)
When sperm and egg
come together via
fertilization, the new cell
is called a zygote
Meiosis
Type of Somatic
Gametes
cell being (body)
(sex) cells
made
cells
Number
of cells
being
made
Chromosome
number
2
4
Diploid
(2N)
Haploid
(N)
Meiosis 1
Interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
I
I
I
M
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Telophase I
Anaphase II
Interphase
Prophase I