Meiosis

• Meiosis is a cell division process where a single (parent) cell divides twice to produce four independent (daughter) cells, each having half the chromosomes as the original cell.
• Meiosis takes place only in the reproductive cell types (sperm and egg cells) of sexually reproducing organisms, including humans.
• For a cell to undergo meiosis, it must have a diploid (2n) chromosome number.
• Meiosis involves two successive stages or phases of cell division, meiosis I and meiosis II.
• Although not a part of meiosis, the cells before entering meiosis I undergo a compulsory growth period called interphase.
• Interphase happens before meiosis starts and is the stage where the cell undergoes growth, DNA replication, and cell functions.
• Prophase I in meiosis involves the formation of a tetrad, crossing over, and the exchange of chromatids.
• Metaphase I in meiosis involves the attachment of spindle fibers to the chromosomes, the alignment of homologous chromosomes in the middle of the cell, and the formation of the nuclear envelope.
• Anaphase I in meiosis involves the pulling of homologous chromosomes to opposite ends of the cell.
• Telophase I in meiosis involves the formation of the nuclear envelope around the chromosomes and the disappearance of the spindle fibers.
• Cytokinesis in meiosis results in the separation of the cell into two new cells.
• Cytokinesis II of meiosis involves both cells separating, forming four new haploid cells.
• Genetic disorders can be chromosomal, affecting the structures that hold your genes/DNA within each cell (chromosomes), or complex (multifactorial), stemming from a combination of gene mutations and other factors.
• In prophase II of meiosis, spindle fibers form and move chromosomes to the center of the cell.
• At the end of meiosis I, two different daughter cells are formed, each with half the number of chromosomes as the parent cell, maintaining the 23 chromosomes in each cell.
• At the end of meiosis II, four non-identical, haploid daughter cells are formed, each having half chromosome number as the original parent cell.
• Anaphase II of meiosis involves fibers pulling the sister chromatids toward opposite ends of the cell.
• The purpose of meiosis is to maintain chromosome number in organisms, create genetic diversity, and repair genetic defects.
• Single-gene (monogenic) conditions occur from a single gene mutation.
• Telophase II of meiosis involves the formation of the nuclear membrane around each chromosome with the disappearance of the spindle fibers.
• Genetic diversity is the biological variation that occurs within species, making it possible for species to adapt when the environment changes.
• Metaphase II of meiosis involves spindle fibers attaching to the chromosomes and chromosomes lining up in the middle of the cell, similar to how they do in Mitosis.
• A genetic disorder is a disease caused in whole or in part by a change in the DNA sequence away from the normal sequence.
• Genetic disorders can be caused by a mutation in one gene, by mutations in multiple genes, by a combination of gene mutations and environmental factors, or by damage to chromosomes.
• Meiosis is a cell division process where a single parent cell divides twice to produce four independent daughter cells, each having half the chromosomes as the original cell.
• Meiosis is also referred to as the reduction division.