In: Facts In the Cell. During meiosis one cell divides twice to form four daughter cells. These four daughter cells only have half the number of chromosomes of the parent cell — they are haploid.
Meiosis produces our sex cells or gametes eggs in females and sperm in males. These are divided between the first time the cell divides meiosis I and the second time it divides meiosis II : Meiosis I 1. Interphase: The DNA in the cell is copied resulting in two identical full sets of chromosomes.
Outside of the nucleus are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.
During interphase, microtubules extend from these centrosomes. Prophase I: The copied chromosomes condense into X-shaped structures that can be easily seen under a microscope. Each chromosome is composed of two sister chromatids containing identical genetic information.
The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on. The pairs of chromosomes may then exchange bits of DNA in a process called recombination or crossing over. At the end of Prophase I the membrane around the nucleus in the cell dissolves away, releasing the chromosomes. The meiotic spindle, consisting of microtubules and other proteins, extends across the cell between the centrioles.
Metaphase I: The chromosome pairs line up next to each other along the centre equator of the cell. The centrioles are now at opposites poles of the cell with the meiotic spindles extending from them. The meiotic spindle fibres attach to one chromosome of each pair. Anaphase I: The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole. In meiosis I the sister chromatids stay together.
This is different to what happens in mitosis and meiosis II. Telophase I and cytokinesis: The chromosomes complete their move to the opposite poles of the cell. At each pole of the cell a full set of chromosomes gather together. A membrane forms around each set of chromosomes to create two new nuclei. The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus.
Cells are the basic building blocks of living things. The human body is composed of trillions of cells, all with their own specialised function. A stem cell is a cell with the unique ability to develop into specialised cell types in the body. In the future they may be used to replace cells and tissues that have been damaged or lost due to disease.
If you have any other comments or suggestions, please let us know at comment yourgenome. Can you spare minutes to tell us what you think of this website? Open survey. In: Facts In the Cell. In metaphase individual chromosomes pairs of chromatids line up along the equator. During anaphase the sister chromatids are separated to opposite poles. During anaphase I the sister chromatids move together to the same pole.
How is vsepr used to classify molecules? What are the units used for the ideal gas law? How does Charle's law relate to breathing? What is the ideal gas law constant? How do you calculate the ideal gas law constant?
How do you find density in the ideal gas law? Does ideal gas law apply to liquids? Impact of this question views around the world. You can reuse this answer Creative Commons License.
0コメント