MITOSIS

• Mitosis is the process in which a eukaryotic cell nucleus splits in two, followed by division of the parent cell into two daughter cells.
• Mitosis consists of distinct phases: prophase, metaphase, anaphase, and telophase. Each phase involves characteristic steps in the process of chromosome alignment and separation.

MITOSIS

• Mitosis is absolutely essential to life because it provides new cells for growth and for replacement of worn-out cells. Mitosis may take minutes or hours, depending upon the kind of cells and species of organisms. It is influenced by time of day, temperature, and chemicals.
• Mitosis is simply described as having four stages—prophase, metaphase, anaphase, and telophase; the steps follow one another without interruption. The entire four-stage division process averages about one hour in duration, and the period between cell divisions, called interphase or interkinesis, varies greatly but is considerably longer.

MITOSIS

• During interphase the chromosomes are dispersed in the nucleus and appear as a network of long, thin threads or filaments, called the chromatin. At some point before prophase begins, the chromosomes replicate themselves to form pairs of identical sister chromosomes, or chromatids; the deoxyribose nucleic acid (DNA) of the chromosomes is synthesized only during interphase, not while mitosis is in process.
• During prophase the two chromatids remain attached to one another at a region called the centromere, but each contracts into a compact tightly coiled body; the nucleolus and, in most cases, the nuclear envelope break down and disappear. Also during prophase the spindle begins to form. In animal cells the centrioles separate and move apart, and radiating bundles of fibers, called asters, appear around them. Some sets of fiber run from one centriole to the other; these are the spindle fibers. In plant cells the spindle forms without centrioles.

MITOSIS

• During metaphase the chromosomes congregate at a plane midway between the two ends to which the spindle tapers. This is called the equatorial plane and marks the point where the whole cell will divide when nuclear division is completed; the ends of the spindle are the poles to which the chromatids will migrate. The chromatids are attached to the spindle fibers at the centromeres.
• During anaphase the two chromatids of each chromosome separate and move to opposite poles, as if pulled along the spindle fibers by the centromeres. During telophase new nuclear envelopes form around the two groups of daughter chromosomes (as they are now called), the new nucleoli begin to appear, and eventually, as the formation of the two daughter nuclei is completed, the spindle fibers disappear. The chromosomes uncoil to assume their dispersed distribution within the interphased nucleus. Cytokinesis, which may begin before or after mitosis is completed, finally separates the daughter nuclei into two new individual daughter cells.

MITOSIS

• Mitosis is important because it is essential for growth and repair in the body

MEIOSIS

• Meiosis is a two-part cell division process that produces sex cells with one half the number of chromosomes as the parent cell. There are two stages or phases of meiosis: meiosis I and meiosis II. At the end of the meiotic process, four daughter cells are produced. Before a dividing cell enters meiosis, it undergoes a period of growth called interphase.
• a nucleus divides into four daughter nuclei, each containing half the chromosome number of the parent nucleus: occurs in all sexually reproducing organisms in which haploid gametes or spores are produced.

MEIOSIS

• The first phase of meiosis involves duplication and then separation of the chromosomes, followed by division into two daughter cells that each contain half the number of chromosomes as the original cell. In the second phase, each daughter cell divides to form an additional reproductive cell.

PROPHASE1

• the start of prophase I, the chromosomes have already duplicated. During prophase I, they coil and become shorter and thicker and visible under the light microscope. The duplicated homologous chromosomes pair, and crossing-over (the physical exchange of chromosome parts) occurs. Crossing-over is the process that can give rise to genetic recombination. At this point, each homologous chromosome pair is visible as a bivalent (tetrad), a tight grouping of two chromosomes, each consisting of two sister chromatids. The sites of crossing-over are seen as crisscrossed nonsister chromatids and are called chiasmata (singular: chiasma).

PROPHASE1

• chromatids and are called chiasmata (singular: chiasma). The nucleolus disappears during prophase I. In the cytoplasm, the meiotic spindle, consisting of microtubules and other proteins, forms between the two pairs of centrioles as they migrate to opposite poles of the cell. The nuclear envelope disappears at the end of prophase I, allowing the spindle to enter the nucleus. Prophase I is the longest phase of meiosis, typically consuming 90% of the time for the two divisions.

METAPHASE 1

• The pairs of homologous chromosomes (the bivalents), now as tightly coiled and condensed as they will be in meiosis, become arranged on a plane equidistant from the poles called the metaphase plate.
• Spindle fibers from one pole of the cell attach to one chromosome of each pair (seen as sister chromatids), and spindle fibers from the opposite pole attach to the homologous chromosome.
• Sister kinetochores of the other homologue pulling those sisters toward the opposite pole.
• bivalents from either parent can align on either side of the cell. In an organism with two sets of chromosomes, there are four ways in which the chromosomes can be arranged, resulting in differences in chromosomal distribution in daughter cells after meiosis I. (A diploid organism with 2n chromosomes will have 2n possible combinations or ways of arranging its chromosomes during metaphase I.)

ANAPHASE 1

• Anaphase I begins when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle. Notice that in anaphase I the sister chromatids remain attached at their centromeres and move together toward the poles. A key difference between mitosis and meiosis is that sister chromatids remain joined after metaphase in meiosis I, whereas in mitosis they separate.

TELEPHASE 1

• During telophase 1 the chromosomes arrive at the poles, decondense, and nuclear membranes re-form around them. In the final stage, the cell physically divides, as in mitotic cytokinesis. The result of the first cell division is two independent cells. One cell contains the maternal homologous pair, or sister chromatids, with a small segment of the paternal chromosome from crossover.
• Despite the small region of crossover, the sister chromatids are still very similar and each cell at this point contains a diploid amount of DNA. The other cell contains the paternal homologous pair with a small segment of the maternal chromosome.

TELEPHASE 1/CYTO 1

• Although diploid cells result from meiosis I, these products are different from those of mitosis because both members of the diploid pair derive from either the maternal or paternal source with the exception of a small section. In mitosis, the cellular division separates sister chromatids and results in diploid cells containing one maternal and one paternal copy in each diploid pair.
• Cytokinesis is the process in which the cell actually divides into two. With the two nuclei already at opposite poles of the cell, the cell cytoplasm separates, and the cell pinches in the middle, ultimately leading to cleavage. In most cells, the mitotic spindle determines the site where the cell will begin to invaginate and split. The first signs of this puckering are usually visible sometime during anaphase.

MEIOSIS 2

• The four main steps of Meiosis II are: Prophase II, Metaphase II, Anaphase II, and Telophase II.

PROPHASE 2

• Prophase II. Meiosis II begins without any further replication of the chromosomes. In prophase II, the nuclear envelope breaks down and the spindle apparatus forms.
• At the end of prophase, the tiny nucleolus within the nucleus dissolves. The nucleolus starts moving towards the nuclear membrane at the beginning of prophase, and its disintegration occurs near the nuclear envelope. Its contents are dispersed in masses.

METAPHASE 2

• Chromosomes align within the equator of the cell to prepare for the division of a cell's nucleus. In humans, 23 of the cell's 46 chromosomes move to one end of the nucleus while the other 23 chromosomes move to the opposite end. Metaphase II aligns the chromosomes so they can move properly towards the opposite ends, notes the Harvard CyberBridge.
• Metaphase II occurs after prophase II and before anaphase II during the overall meiosis II process, according to the Harvard CyberBridge. The amount of chromosomes in cells do not change during meiosis II. Meiosis produces egg cells in human females and sperm cells in human males, and meiosis is ultimately responsible for passing genetic information to offspring.

METAPHASE 2

• Spindles form within a cell's nucleus, and single chromosomes align perpendicularly to the spindles, notes Pearson Education. This is unlike metaphase I, a process that involves the alignment of chromosome pairs rather than single chromosomes. At the end of metaphase II, chromosomes attach to small tubules at the poles of each cell nucleus to prepare for the next phase.

ANAPHASE 2

• In anaphase 2, the centromeres are cleaved down the middle allowing microtubules to attach to the kinetochores which pulls the sister chromatids apart. The centromeres are the center part of the sister chromatids that hold them together, often represented by a dot or a circle. When this is broken, the two separate. The sister chromatids are now called sister chromosomes as they move toward opposing poles and are no longer together. By this time, the cell is almost ready to completely separate into daughter cells, resulting in four overall daughter cells by the end of meiosis 2.

TELOPHASE 2

• Telophase is the final stage of mitosis, or the process by which cells divide. Mitosis consists of five phases - prophase, prometaphase, metaphase, anaphase, and telophase. During telophase, the nuclei for the daughter cells finally form and the cell begins to split into two.
• Cytokinesis takes place, producing four daughter cells (gametes, in animals), each with a haploid set of chromosomes. Because of crossing-over, some chromosomes are seen to have recombined segments of the original parental chromosomes.

TELOPHASE 2

• The division of the cytoplasm and the plasma membrane following the division of the nucleus resulting into two cells, each having its own nucleus and cytoplasm surrounded by a plasma membrane.

This pictures shows how the cells separate from one another in meiosis

THIS IS OF THE CYCLE OF MEIOSIS IN MALES.

This compare and contrasts mitosis and meiosis

THIS DIAGRAM SHOWS THE LIFE CYCLE OF A CELL

MEIOSIS VS MITOSIS

• They are both similar because both are a type of cell division,both have no new gene combinations when each new cell splits both are involved in DNA replication, and both have inter, pro, meta, ana, and telophases

MEIOSIS VS MITOSIS

• They are both similar because both are a type of cell division,both have no new gene combinations when each new cell splits both are involved in DNA replication, and both have inter, pro, meta, ana, and telophases

MITOSIS VS MEIOSIS

• They are different because Mitosis occurs in somatic cells and meiosis occurs in reproductive cells,dividing cells in mitosis can be either diploid or haploid but in meiosis, the dividing cells can only be diploid in mitosis, two daughter cells are formed but in meiosis, four daughter cells are formed,mitosis helps in growth and in body repairs but meiosis helps in sexual reproduction and regulation of the number of chromosomes In mitosis, cytokinesis occurs only once, but in meiosis, cytokinesis may take place once or twice.

MITOSIS AND MEIOSIS

• In conclusion I feel they are both very important processes in our body that help us produce more cells, grow, repair (mitosis), and reproduce (meiosis).