A few eukaryotes, notably the Bdelloid rotifers, have lost the ability to carry out meiosis and have acquired the ability to reproduce by parthenogenesis. Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually. In animals, meiosis always results in the formation of gametes, while in other organisms it can give rise to spores. In biology or life science, meiosis (pronounced my-oh-sis) is a process of reductional division in which the number of chromosomes per cell is cut in half. Risk calculators and risk factors for MeiosisД®vents involving meiosis, showing chromosomal crossover US National Guidelines Clearinghouse on Meiosis Four genetically unique daughter cells are produced.Articles on Meiosis in N Eng J Med, Lancet, BMJ Nuclear envelope reforms and cytokinesis takes places. Telophase II: chromatids reach opposite poles of the cell. Metaphase II: chromosomes attach to the spindle fibre by their centromeres.ДЄnaphase II: sister chromatids are separated. Prophase II: chromosomes condense, nuclear envelope disintegrates and spindle fibres form. Cytokinesis results in the formation of two daughter cells. Nuclear envelope reforms around the chromosomes. Telophase I: chromosomes reach opposite poles of the cell. Metaphase I: homologous chromosomes line up along the equator and attach to the spindle fibre by their centromeres.ДЄnaphase I: homologous chromosomes are separated The nuclear envelope disintegrates and spindle fibres form. Prophase I: chromatids condense and arrange themselves into homologous pairs (called bivalents). Interphase: the DNA replicates so there are now two identical copies of each chromosome (referred to as chromatids). Meiosis involves two rounds of cell division which are referred to as meiosis I and meiosis II. When two haploid gametes join during fertilisation, a diploid cell called a zygote is formed. Unlike mitosis, the daughter cells are genetically different from the parent cell and contain just half the number of chromosomes (i.e. Meiosis is the type of cell division which produces gametes for sexual reproduction.

The cytoplasm divides ( cytokinesis) and the plasma membrane pinches off to form two new, genetically-identical cells. Telophase & cytokinesis - the two groups of chromsomes decondense (they become long and thin) and a nuclear envelope reforms around them, forming two new nuclei. They attach to the spindle fibre by their centromere.ДЄnaphase - the centromere splits and the chromatids are pulled to opposite poles of the cell. Metaphase - the chromosomes line up along the middle of the cell. The centrioles move to opposite poles of the cell and form spindle fibres. Prophase - the chromosomes condense (they become shorter and fatter) and the nuclear envelope disintegrates. The mitochondria produce more ATP which will provide the energy for cell division. Once the DNA has replicated, each chromosome now consists of two sister chromatids, connected by a structure called the centromere. Interphase - the cell prepares for mitosis by growing larger, replicating its organelles and synthesising new DNA (see above).

Prophase i of meiosis