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What Procedure Represents the Process of Meiosis?

Meiosis is a process of cell division in animals that creates germ cells (either an egg or sperm) for sexual reproduction. This process differs from mitosis, which is the procedure that reproduces the other cells in the body. When mitosis occurs, one cell with 46 chromosomes divides and creates two cells that also have 46 chromosomes each. With meiosis, the cell divides its chromosomes in half and results in four cells with 23 chromosomes each. This procedure of cell division involves two distinct phases.

Prophase I
- A chromosome magnified 400 times
  
  Inside the cell̵7;s nucleus, matching chromosomes pair up with one another and then split in half to create chromatids or one-half of a chromosome. At this point, nonsister chromatids can connect and trade sections. This trading is called ̶0;crossing over̶1; and creates genetic variances.
Metaphase I
- In Metaphase I, the chromosome pairs line up randomly at the cell equator, which further increases genetic variance.
Anaphase I
- Spindle fibers can be observed under a microscope when the chromatids begin migrating to opposite poles of the cells.
  
  In Anaphase I, the sister chromatids break apart and begin moving toward opposite poles.
Telophase I
- A cleavage furrow forms between each set of chromosomes in Telophase I. The two resulting cells are haploid; they have half of the chromosomes of the original diploid cell.
Prophase II
- The nuclear membrane dissolves at the beginning of the second phase of meiosis. The cell division process starts over. Spindle formation begins as chromosomes start to pair.
Metaphase II
- In Metaphase II, the chromatid pairs line up at each equator.
Anaphase II
- The pairs pull apart and move toward their respective poles in Anaphase II.
Telophase II
- A cleavage furrow forms again between each set of chromosomes in Telophase II. Now there are four haploid cells (or gametes) each with 23 chromosomes.
Gamete Cells
- In this DNA model, half of the ladder represents the 23 chromosomes from each parent.
  
  When one of these haploid cells fuses with a gamete from the opposite sex (fertilization), they create a zygote with 46 chromosomes.

Animals & Science