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Meiosis Notes
You have two types of cells in your body
_____________ cells are your body cells, they make up most of your body tissues and organs.
Germ cells are in your reproductive organs that develop into ______________ (sex cells).
Every species has a characteristic number of chromosomes per cell.
Humans have _____ chromosomes or _____ pairs.
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 ______________)
___________________________ involves the fusion of two gametes, resulting in
offspring that are a genetic mixture of both parents.
______________________- The nuclei of the sperm and egg cell fuse together to
form one nucleus.
Diploid Cells
Haploid Cells
The cell has two copies of each
chromosome
A cell has only one copy of each
chromosome
1 from the Mother
1 from the Father
Each human egg or sperm has a total of
23 chromosomes. (22 autosomes and 1
sex chromosome)
For humans, the diploid number is 46
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.
- Germ cells in reproductive organs undergo the process of meiosis to
form _______________
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- The homologous chromosomes, or sister
chromatids do not separate properly during cell division.
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