NOTE:
Diploid =
Has BOTH mom AND dad’s chromosome
Example:
In a cell, if it has chromosome number 1 for dad and chromosome number 1 for mom
Haploid =
Has EITHER
Mom OR dad’s chromosome
Example:
In a cell, if it has chromosome number 1 for dad or chromosome number 1 for mom, but not both
MEIOSIS I
Interphase
- Growth to maturity (G1)
- DNA replication (S)
46 single to 92 single
- copies of both mom and dad (diploid)
- Replication of organelles (G2)
Prophase I
- Homologous chromosomes pair to form tetrad by synapsis
- Crossing over can occur
- Centrioles spread and spindles extend
- Polar spindles extend centriole to centriole
- Kinetochore spindles attach to centromeres of each double chromosome
Metaphase I
- tetrads are organized in the middle of the cell
- crossing over could occur
Anaphase I
- Spindles retract pulling the homologous chromosomes to opposite sides of the cell (disjunction) allowing independent assortment by
- Cleavage furrow is obvious
Telophase I
- Cleavage furrow continues until cytokinesis occurs
- 2 haploid cells form. They have, for ex, double chromosome 1 of mom or dad, not both in the same cell.
CHROMO-
SOME NUMBERS (MEIOSIS)
46 single
92 single
46 double (23 double mom and 23 double dad)
Homologous chromosomes find to make 23 tetrads
23 tetrads (total 46 chromosomes)
23 double chromosomes to one side, 23 double to the other side (random)
2 cells (23 double chromosomes in each, but mom’s double chromo. 1 in one cell, dad’s double chromo. 1 in another cell…haploid
CHROMO-
SOME NUMBERS (MITOSIS)
46 single (diploid)
92 single
46 double
46 double
46 single to one side and 46 single to other side
46 single in each cell (23 single mom and 23 single dad in
each cell.. diploid)
MITOSIS
Interphase
- Growth to maturity (G1)
- DNA replication (S)
46 single to 92 single
- copies of both mom and dad (diploid)
- Replication of organelles (G2)
Prophase
- Chromosomes pair to double chromosomes (made of identical single chromosomes)
- Centrioles spread and spindles extend
- Polar spindles extend centriole to centriole
- Kinetochore spindles attach to centromere
Metaphase
- Double chromosomes are organized in the middle of the cell
Anaphase
- Spindles retract pulling the chromatids (now single chromosomes) apart to opposite sides of the cell.
- Cleavage furrow is obvious
Telophase
- Cleavage furrow continues until cytokinesis occurs
- 2 identical cells form. They have copies of both mom and dad’s chromosomes (diploid)
MEIOSIS II
Begin with 2 haploid cells (example: one cell has mom’s chromosome 1 and the other cell has dad’s chromosome 1…..if the cell has mom or dad’s then haploid
Prophase II
- Double chromosomes present (mixture of mom and dad)
- Centrioles spread and spindles extend
- Polar spindles extend centriole to centriole
- Kinetochore spindles attach to centromere
Metaphase II
- Double chromosomes are organized in the middle of each cell
Anaphase II
- Spindles retract pulling the chromatids (now single chromosomes) apart to opposite sides of the cell.
- Cleavage furrow is obvious
Telophase II
- Cleavage furrow continues until cytokinesis occurs
- 4 haploid sex cells form. In men, 2 are same as each other, while the other 2 are the same as one another.
CHROMO-
SOME NUMBERS (MEIOSIS)
2 cells with 23 double in each (haploid)
2 cells with 23 double in each (haploid)
2 cells with 23 single to one side and 23 single to other side of each cell
23 single in each of the 4 cells (haploid)