mitosis

• Meiosis, also known as reduction division, is the type of cell division that produces gametes, such as sperm cells in males and egg cells in females.
• Meiosis is broken down into two stages of cell division called Meiosis I and Meiosis II.
• During Meiosis I, there are four phases: Prophase I, Metaphase I, Anaphase I, and Telophase I.
• In Meiosis II, there are four phases: Prophase II, Metaphase II, Anaphase II, and Telophase II.
• During Prophase I, the chromatin of a diploid cell contains two uncoiled spread out sets of chromosomes inherited from each parent.
• The replicated DNA in the chromatin condenses into the more familiar X-shaped chromosomes.
• The replicated DNA is the same in the identical sister chromatids of each chromosome.
• In a process called synapsis, each chromosome pairs up with and binds to its corresponding homologous chromosome forming a tetrad.
• The chromosomes contain genetic information called genes, which were inherited from each parent and different versions of the same gene on each chromosome are called alleles.
• Chromatids from each homologous chromosome exchange segments of alleles during a process called crossing over, resulting in different gene combinations.
• Crossing over randomly happens on every chromosome, explaining why every gamete is genetically different from every other gamete.
• During Prophase I, the nuclear membrane disappears, the centrioles move to opposite ends of the cell, and spindle fibers fan out from them.
• During Metaphase I, the homologous chromosomes line up at the equator and attach to spindle fibers from opposite poles.
• During Anaphase I, spindle fibers separate the homologous chromosomes in each tetrad and pull them to opposite poles of the cell.
• The cell enters Telophase I with one chromosome from each homologous pair at separate poles.
• Each chromosome still consists of sister chromatids, but they're no longer identical because of the allele exchange that happened during crossing over.
• Spindle fibers disappear and the nuclear membrane reforms around the chromosomes during Telophase I.
• Cytokinesis occurs in Meiosis I, producing two genetically different haploid daughter cells each containing chromosomes in the form of paired sister chromatids.
• During Prophase II, the nuclear membrane disappears and spindle fibers fan out from the two sets of paired centrioles.
• During Metaphase II, the chromosomes in each cell line up at the equator and attach to spindle fibers from both poles.
• During Anaphase II, the sister chromatids of each chromosome separate and move to opposite poles.
• During Telophase II, the spindle fibers disappear and nuclear membranes reform and cytokinesis occurs in both cells.
• Meiosis II ends with four genetically different haploid daughter cells each containing only one set of chromosomes.
• During Prophase I, the pairing of homologous chromosomes called synapsis occurs, with each pair of homologous chromosomes consisting of four chromatids called a tetrad.
• Crossing over results in genetic differences in gametes, with all gametes produced by meiosis being haploid.