The Cell Cycle And Dna Replication

In most eukaryotes, the nuclear envelope that separates the DNA from the cytoplasm disassembles. The chromosomes align themselves in a line spanning the cell. As the cell elongates, corresponding sister chromosomes are pulled toward opposite ends.

Meiosis consists of one DNA replication and two nuclear divisions resulting in 4 daughter cells. The process which provides for genetic variation is crossing over. Crossing over occurs in the early stages when homologous chromosomes move together so that their chromatids form a tetrad. This is called synapsis and allows for the exchange of chromosome sections.

Mitosis: This is the process by which a cell duplicates the chromosomes in its cell nucleus in order to generate two identical daughter nuclei.

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.

A) Meiosis consists of two cell divisions and is broken up into Meiosis I and Meiosis II. At the beginning of the Cell Cycle, in this case there are four chromatids each from the homologous pairs being A, a, B, b. This is the Diploid number (4) meaning it is 2 times the haploid number that will be seen at the end of meiosis II. During the S phase of interphase, the chromatids replicate and reach the end of G2 phase. Now starting meiosis, during the first stage of prophase I the chromosomes condense and pair up through synapsis with their sister chromatids creating AA, aa, BB, bb. After they pair up they go through a process called crossing over, where the homologous chromosomes share a piece of their genetic material with each other. Crossing over allows for the genetic diversity of chromosomes. Now there are four homologous chromosomes Aa, Aa, Bb, Bb, each containing heterozygous alleles because the sister chromatids exchanged genetic information with their homologous pair. During late prophase I, spindle fibers being to form where they will later attach to a homologous chromosomes centromere. The next stage is Metaphase I. During metaphase I, the homologous pairs line up at the metaphase plate, also known to be the center of the cell. The homologous pairs form a tetrad which is considered a group of four homologous chromosomes. These homologous chromosomes orient themselves randomly, which is know as the process of independent

Mitosis is the process of duplicating nuclear material one cell becomes two cells. A cell contains 46 chromosomes, this is known as diploid. This process involves prophase, metaphase, anaphase, and telophase. Mitosis ensures the continuation of the organism and helps the body build and repair. Meiosis on the other hand is for production of haploid cells, 23 chromosomes, that together with another human, new organisms are created.

This study was performed in order to gain more knowledge on mitosis and meiosis. This lab was done by observing mitosis in plant and animal cells, comparing the relative lengths of the stages of mitosis in onion root tip cells, stimulating the stages of meiosis, observing evidence of crossing-over in meiosis using Sordaria fimicola, and estimating the distance of a gene locus from its centromere. Mitosis is the scientific term for nuclear cell division, where the nucleus of the cell divides, resulting in two sets of identical chromosomes. Mitosis is accompanied by cytokinesis in which the end result is two completely separate cells called daughter cells. There are four phases of mitosis: prophase, metaphase, anaphase and

Mitosis - the division of a cell 's nucleus resulting in two daughter nuclei, each with the same number of chromosomes as the original nucleus.

In genetics, the way people retrieve their genes and traits is through cell division; mitosis and meiosis. Mitosis in cell division is the process in making body cells. There are 7 stages in mitosis; interphase, prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis. In interphase, the cell is growing normally and synthesizes with organelles. In prophase, changes occur in the cell and parts of the structures begin to break down, setting the stage for chromosome division. Prometaphase is the stage where the chromosomes are sorted and made very compact, and metaphase is when the chromatids of each chromosome are attached to a microtube to form a spindle. Anaphase it the process in which the chromosomes split, leading into telophase, which is where the chromatids travel to opposite poles in a cell and new membranes form around the nuclei. The final stage in mitosis, cytokinesis, is when the chromatids split in two.

Mitosis produces two cells, identical to each other and the parent cell. This means that each chromosome is copied exactly. During the mitosis cell cycle there are 6 stages, Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis. Sometimes the cell divide uncontrollably. This results in a large mass of cells called a tumor. If tumor successfully gets into other body tissue the result is

When this checkpoint is passed, cdk4 and cyclin D interact. This interaction results in phosphorylation of the retinoblastoma protein, which in turn allows activation of the transcription factor E2F. Active E2F promotes expression of the cyclin E gene. Cyclin E (protein) and cdk 2 interact to

The cell cycle refers to sequence of events that takes place in a cell leading to its division and duplication (replication). This process is important to genetics because through the cell cycle genetics information for all sorts are passed from parents to daughter cells. (Griffiths. A et al)

Sample response: Graph A represents a cell undergoing meiosis and Graph B represents a cell undergoing mitosis. In both mitosis and meiosis, the cell starts out with a certain mass of DNA that then doubles as DNA replication takes place during interphase. In mitosis, the cell undergoes the next set of stages including prophase, metaphase, and telophase without changing the quantity of DNA in the cell. When mitosis reaches telophase, the cell divides in two and so one-half of the DNA goes into one daughter cell and the other half goes into the other daughter cell. This results in two daughter cells with the same quantity of DNA as was present in the parent cell. In meiosis I, this same pattern of DNA mass change takes place as DNA replicates

The chromosomes are replicated and each is reported to comprise "two identical chromatids" which are stated to be joined by a centromere, which is a stretch of DNA. The first round of division or Meiosis is the division that divides homologous chromosomes. The second round of division, or Meiosis II divides sister chromatids resulting in four haploid cells each of which contain a different gene mix. (Hartwell, 2006, paraphrased) This is illustrated in Figure 2.

The process of DNA replication plays a crucial role in providing genetic continuity from one generation to the next. Knowledge of the structure of DNA began with the discovery of nucleic acids in 1869. In 1952, an accurate model of the DNA molecule was presented, thanks to the work of Rosalind Franklin, James Watson, and Francis Crick. To reproduce, a cell must copy and transmit its genetic information (DNA) to all of its progeny. To do so, DNA replicates following the process of semi-conservative replication. Two strands of DNA are obtained from one, having produced two daughter molecules that are identical to one another and to the parent molecule. This essay reviews the three stages