Essay Mitosis and Meiosis
926 Words4 Pages
Cell division may happen by either mitosis or meiosis, depending on what type of cell is invovled. Mitosis is a process by which a cell divides to form two daughter cells. They each have the same exact number and kind of chromosomes as the parent cell. Meiosis occurs in the primary sex cells leading to the formation of viable egg and sperm cells. They reduce the number of chromosomes to half in each gamete so that when they are getting furtilized, the species chromosome number is kept even.
Mitosis happens in the reproduction of unicellular organisms and in the addition of cells to a tissue or organ in a multicellular organism.
There are four stages of mitosis. The first stage is the prophase. In this stage the chromosomes become shorter…show more content…
The spindle fibers extending from the poles to the centromeres disappear and those fibers that lie in the plane between the rows of chromosomes remain for a longer time. A nuclear membrane reforms around each bundle of chromosomes at the poles. At the center of animal cells, the cytoplasm turns inward, pinching the old cell into two new cells.
Meiosis happens in the primary sex cells, which leads to the formation of viable egg and sperm cells. The purpose of meiosis is to cut the number of chromosomes in half.
There are two stages of meiosis, meiosis I and II. Meiosis I has five stages called prophase I, metaphse I, anaphase I, telophase I, and interkinesis I. Meiosis II has only four stages. They are prophase II, metaphase II, anaphase II, and telophase II.
The stages of meiosis I result in the reduction of the number of chromosomes.
In prophase I the chromosomes become shorter and thicker and the nucleolus disappears. The chromosomes pair with their homologues forming a group of four chromatids. The tetrads wrap around each other and may exchange like parts. The centrioles move and the spindle fibers appear and the nuclear membrane disappears.
The tetrads move as a group to the equator in metaphase I. The centromeres of each of the homologous pairs of chromosomes become attached to spindle fibers extending from opposite poles.
Each pair of double-stranded chromosomes, in anaphaseI, is pulled away from its homologue
Compare and Contrast Mitosis and Meiosis Essay
496 Words2 Pages
Compare and Contrast Mitosis and Meiosis
Meiosis and mitosis describes the process by which cells divide, either by asexual or sexual reproduction to produce a new organism.
Meiosis is a form of cell division that produces gametes in humans these are egg cells and sperms, each with reduced or halved number of chromosomes. The number of chromosomes is restored when two gametes fuse together to form a zygote. A cell with two copies of each chromosome is called diploid cell and a cell with one copy of each chromosome is called a haploid cell. Meioses produces haploid daughter cells that are genetically different from each other and from the parent cell. However, mitosis is a form of cell division that produces daughter cells…show more content…
These bivalents line up along the equator during metaphase I, the arrangement of the bivalent is completely random and relative to the orientation of the other bivalents, this is known as the independent assortment of chromosomes. This is followed by anaphase I where the homologous chromosomes separate and move to the opposite poles of the cell.
At telophase I the cell divides into two, each cell contains one chromosome from each homologous pair. The second stage of meiosis is similar to mitosis. These centrioles replicate and the chromosomes line along the equator at metaphase II and spilt at the centromeres causing the chromatids to move to opposite sides at anaphase II. At telophase II the cell divides to form four haploid cells, these are not identical to each other because the cells contains chromosomes from two different parent gametes therefore differ genetically.
However, during mitotic division the cells produced are genetically identical to each other because they are produced from the same parent cell. The cell begins to replicate during interphase to produce two identical sister chromatids. At prophase the chromosomes become condense to become visible and the membrane begins to break down. The chromosomes line up along the centre of the equator during metaphase.
The chromatids separate and are pulled to opposite poles during anaphase. In telophase these separate chromatids