Meiosis - Meiosis: Its Stages (GCSE Biology)
Meiosis: Its Stages
Stages of Meiosis
There are two divisions in meiosis – meiosis 1 and meiosis 2:
- DNA duplicates. Each chromosome has a copy of itself.
- The chromosomes line up at the equator in pairs. One from the mother and one from the father.
- The cell undergoes the first division in meiosis 1. The pairs of chromosomes are pulled apart. Some of the mother’s chromosomes and some of the father’s chromosomes go into the new cells, creating a mixture of their chromosome. This mixes up the genes and creates genetic variation in the offspring.
- The chromosomes line up at the equator again in both cells.
- The 2 cells undergo the second division in meiosis 2. The arms of the chromosomes (chromatids) are pulled apart.
- The gametes are made as 4 haploid daughter cells. Each of the gametes is genetically unique from one another and they only have a single set of chromosomes (23 chromosomes). Hence, they are haploid.
Meiosis is a type of cell division that results in the production of four genetically different daughter cells from a single parent cell. It is the process that produces reproductive cells, such as sperm and eggs, for sexual reproduction.
The stages of meiosis are: Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis I, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis II.
During Prophase I, the chromosomes condense and become visible. They also exchange genetic material in a process called crossing over, which helps to increase genetic diversity.
During Metaphase I, the chromosomes line up at the equator of the cell and are pulled apart by microtubules to opposite poles of the cell.
During Anaphase I, the sister chromatids separate and are pulled to opposite poles of the cell by the spindle fibers.
During Telophase I, a nuclear envelope forms around each set of chromosomes, creating two separate nuclei in the same cell.
During Cytokinesis I, the cell divides into two daughter cells, each with a set of chromosomes identical to those of the parent cell.
During Prophase II, the chromosomes condense and become visible again.
During Metaphase II, the chromosomes line up at the equator of the cell and are pulled apart by microtubules to opposite poles of the cell.
During Anaphase II, the sister chromatids separate and are pulled to opposite poles of the cell by the spindle fibers.
During Telophase II, a nuclear envelope forms around each set of chromosomes, creating two separate nuclei in the same cell.
During Cytokinesis II, the cell divides into two daughter cells, each with a unique combination of chromosomes from the parent cell. This results in the production of four genetically different daughter cells.
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