Meiosis Notes
You have two types of cells in your body
Somatic Cells-
Germ Cells-
Every species has a characteristic number of chromosomes per cell.
Chromosomes 1-22 make up your _____________
(characteristics not related to your sex)
The 23rd pair of chromosomes are your sex chromosomes
(XX for _______________
XY for ______________)
Sexual Reproduction-
Fertilization-
Diploid Cells
The cell has two copies of each
chromosome
1 from the Mother
1 from the Father
For humans, the diploid number is 46
Haploid Cells
A cell has only one copy of each
chromosome
Each human egg or sperm has a total of
23 chromosomes. (22 autosomes and 1
sex chromosome)
Organism
Human
Diploid (2n)
Haploid (n)
46
23
Chimpanzee
24
Elephant
56
Garden Pea
14
Turkey
Polar Bear
Pineapple
40
74
25
Meiosis- A from of nuclear division that divides a diploid cell into a haploid cell.
Gametes-
Meiosis 1
Prophase 1
-
Chromatin  Chromosomes
Nuclear membrane breaks down
Homologous chromosomes pair up
Crossing over may occur
Metaphase 1
-
Homologous chromosomes are randomly
lined up along the middle
Anaphase 1
-
Paired homologous chromosomes separate
Sister chromatids stay together during meiosis 1
Telophase 1
-
Nuclear membrane reforms
Spindle fibers disassemble
Cytokinesis
There is no Interphase after cytokinesis: Chromosomes
do NOT duplicate
Meiosis 2
Prophase 2
-
Nuclear membrane breaks down
Chromosomes condense
Spindle fibers assemble
Metaphase 2
-
Spindle fibers align the 23
Chromosomes in the middle
-
Each chromosome still has
2 sister chromatid
Anaphase 2
-
The sister chromatids are pulled apart
Telophase 2
-
Nuclear envelop reforms
Spindle fibers break apart
Cytokinesis
Nondisjunction-
Stages
Characteristic
Interphase
DNA Synthesized
Prophase
-Nucleus
Dissolves
-DNA condenses
Metaphase
Chromosomes
line up in the
middle
Anaphase
Chromosomes
pull apart
Telophase
Nucleus reforms
Cytokinesis
How many
daughter cells are
created?
Mitosis
Meiosis 1
Meiosis 2