How are sperm and egg cells formed?
Describe in general terms what happens during meiosis.
no
I don't know what your "no" post means, but here is information on meiosis.
http://www.google.com/search?client=safari&rls=en&q=meiosis+animation&ie=UTF-8&oe=UTF-8
I hope this helps.
Sperm and egg cells, also known as gametes, are formed through a process called meiosis. Meiosis is a specialized type of cell division that occurs in the reproductive organs of organisms, including humans.
During meiosis, the diploid cells, which have two sets of chromosomes (one set from each parent), undergo two rounds of cell division, resulting in the formation of four haploid cells. Haploid cells contain only one set of chromosomes, as opposed to the two sets found in diploid cells.
Let's break down the general steps of meiosis:
1. Interphase: Before meiosis begins, the cell undergoes a period of growth and DNA replication. This stage is called interphase.
2. Meiosis I: The first division of meiosis is called Meiosis I. It involves four distinct phases: prophase I, metaphase I, anaphase I, and telophase I.
- Prophase I: During this phase, the chromosomes condense and pair up with their homologous counterparts. This pairing is known as synapsis. Each pair of homologous chromosomes forms a structure called a tetrad. Crossing-over, a process where genetic material is exchanged between non-sister chromatids, occurs during this phase.
- Metaphase I: The tetrad aligns along the center of the cell, known as the metaphase plate, with spindle fibers attaching to each chromosome.
- Anaphase I: The homologous chromosomes separate and move towards the opposite ends of the cell.
- Telophase I: The cell begins to divide, and two daughter cells start forming, each containing one set of chromosomes.
3. Meiosis II: The second division of meiosis is called Meiosis II. This division is similar to a regular cell division (mitosis) and consists of prophase II, metaphase II, anaphase II, and telophase II.
- Prophase II: The chromosomes, still consisting of two sister chromatids, condense, and the nuclear envelope disintegrates.
- Metaphase II: The chromosomes align along the metaphase plate, and spindle fibers attach to each chromatid.
- Anaphase II: The sister chromatids separate and move to opposite poles of the cell.
- Telophase II: The cell encloses, and the nuclear envelope forms around the four resulting haploid cells, each containing a unique combination of chromosomes.
Ultimately, the final products of meiosis are four haploid cells called gametes, such as sperm or eggs. The specific process and variations of meiosis can differ between organisms, but the overall goal is to ensure the formation of genetically diverse gametes, allowing for genetic variation in offspring.