Cell Division Flashcards
Whats mitosis?
2 cells are formed.
Same number and type of chromosomes as the original cell.
Mitosis forms all cells in our bodies except the gametes.
What are the stages of mitosis?
IPMATC
1) Interphase - The chromosomes duplicate and become 2 identical chromatids, they then join at the centromere.
2) Prophase - In the nucleus the chromosomes condense and in the cytoplasm spindle fibers form.
3) Metaphase - The nuclei membrane breaks apart, the spindle fibers attach to the chromosomes and the chromosomes line up at the equator of the cell.
4) Anaphase - The spindle fibers shorten and the centromere divides so that each chromosome becomes 2 separate chromatids.
5) Telophase - The nuclei membrane forms around each set of chromosomes. The chromosomes then spread back out into the new nucleus and the spindle fibers break down.
6) Cytokinesis - The cell membrane pinches into 2 separate sets of chromatids and into 2 identical daughter cells.
Whats meiosis?
4 cells are formed.
Forms gametes.
Takes place in 2 stages called meiosis I and meiosis II.
Each daughter cell is genetically different from the other.
What occurs in meiosis I?
1) Interphase: Before meiosis begins, the cell undergoes a period of growth called interphase. During interphase, the DNA of the chromosomes is replicated.
2) Prophase I: Where crossing over occurs. Each of the homologous pairs line up side by side, while this happens segments of the chromosomes are exchanged. This process is responsible for genetic diversity.
The spindle apparatus form.
3) Metaphase I: The homologous pairs align on either side of the cell.
4) Anaphase I: The spindle fiber contracts and pulls the homologous pairs, each with 2 chromatids, away from each other and towards each pole of the cell.
What occurs in meiosis II?
1) Telophase I & Cytokinesis: The cell now undergoes a process called cytokinesis that divides the cytoplasm of the original cell into 2 daughter cells. Each daughter cell is haploid and has only 1 set of chromosomes, or half of the total number of chromosomes of the original cell.
2) Prophase II: Chromosomes condense and the nuclear envelope breaks down. The centrosomes move apart , the spindle forms between them and the spindle microtubules begin to capture chromosomes.
3) Metaphase II: The chromosomes align themselves along the metaphase plate through the facilitation of the spindle fibers.
4) Anaphase II: The centromere splits, freeing the sister chromatids from each other. At this point the spindle fibers begin to shorten, pulling the newly separated sister chromatids towards opposite ends of the cell.
5) Telophase II & Cytokinesis:
The cells pinch in the center and divide again. The final outcome is 4 cells, each with half of the genetic material found in the original. For males, each cell becomes a sperm, and for females an egg. And the other 3 become polar bodies which arent used.
How are identical twins formed?
Identical twins are formed from the same zygote.
When the zygote divides by mitosis, the 2 genetically identical cells formed don’t stay together.
Instead they separate and each cell behaves as though it were an individual zygote, dividing and developing into an embryo.
