Download The Meiosis Cell Cycle

The Meiosis Cell Cycle
A. Chromosome Number
1. Every species has a specific number
of chromosomes
2. Humans have 46 chromosomes in
their cells ~ half from mom, half from
dad
3. Homologous
Chromosomes
a. pairs of
chromosomes (one
from mom and one
from dad) that are
similar but not
exactly the same
b. Humans have 46
chromosomes, or
23 pairs of
homologous
chromosomes.
4. Diploid Cells
a. Cells that have a full set of chromosomes
b. In humans, the diploid number is 46.
i.
Diploid number is abbreviated 2N, so for
humans, we say that 2N = 46.
5. Haploid Cells
a. Cells that have half the number of
chromosomes
b. In humans, the haploid number is 23
i.
Haploid number is abbreviated N, so for
humans, we say that N = 23.
B. The mitosis cell cycle
1. A type of cell division that produces
somatic cells
a. Somatic Cells = all body cells
i. Liver, heart, skin, etc.
ii. Diploid cells
iii. Genetically identical to each other (have the
same DNA)
C. The meiosis cell cycle
1. Special type of cell division that
produces gametes
a. Gametes = sex cells
i. egg and sperm
ii. Haploid ~ have half the number of
chromosomes. Why?
23
+
23
=
46
iii. Gametes are genetically different from each other.
2. Meiosis cell cycle begins with one
diploid cell and ends with the production
of 4 haploid cells that are genetically
different from each other and the
mother cell
a. Crossing over = when homologous
chromosomes swap sections of DNA. This
is one source of genetic variation
= from Mom
= from Dad
D. Stages of the Meiosis Cell Cycle
I.
The Meiosis Cell Cycle
A.
Interphase
1.
G1
2.
S
3.
G2
B.
Cell Division
1.
Meiosis I
a. Prophase I
b. Metaphase I
c. Anaphase I
d. Telophase I and cytokinesis
2.
Meiosis II
a. Prophase II
b. Metaphase II
c. Anaphase II
d. Telophase II and Cytokinesis