Describe the sequence of the cell cycle?
um first there is interphase, and in interphase there is the G1 phase, S phase, and G2 phase. Then there is Mitosis and that is prophase, metaphase, anaphase, telophase/cytokinesis. and the cytoplasm divides and 2 new cells are created and the cell cycle continues over and over again
LIST THE PHASES OF THE CELL CYCLE WITH A BRIEF DESCRIPTION OF WHAT OCCURS IN EACH PHASE?
G1 phase - growth and synthesis. Gap phase 1 begins at the completion of mitosis and cytokinesis and lasts until the beginning of S phase. This phase is generally the longest of the four cell cycle phases and is quite variable in length. During this phase, the cell chooses either to replicate its deoxyribonucleic acid (DNA) or to exit the cell cycle and enter a quiescent state (the G0 phase). S phase Replication of the chromosomes is restricted to one specific portion of interphase, called S phase (DNA synthesis phase), which typically lasts about 6 h. In mammalian cells, the start of S phase—the actual initiation of DNA synthesis—takes place several hours after the cell has committed to carrying out DNA synthesis. During S phase, each chromosome replicates exactly once to form a pair of physically linked sister chromatids. In animal cells, a pair of centrioles is also duplicated during S phase. G2 phase - Preparation for division The portion of interphase that follows S phase is called gap phase 2. Some cells can exit the cell cycle from G2 phase, just as they can from G1 phase. M phase M phase includes the overlapping processes of mitosis and cytokinesis. Mitosis is divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis usually begins during anaphase and ends at a point after the completion of mitosis. At the end of cytokinesis, the parent cell has formed its two G1 phase progeny and the cell is ready to repeat the cycle.
Describe the main result of meiosis?
biology, meiosis (pronounced /maɪˈoʊsɨs/) is a process of reductional division in which the number of chromosomes per cell is cut in half. In animals, meiosis always results in the formation of gametes, while in other organisms it can give rise to spores. As with mitosis, before meiosis begins, the DNA in the original cell is replicated during S-phase of the cell cycle. Two cell divisions separate the replicated chromosomes into four haploid gametes or spores. Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually. 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 does not occur in archaea or bacteria, which reproduce via asexual processes such as binary fission. During meiosis, the genome of a diploid germ cell, which is composed of long segments of DNA packaged into chromosomes, undergoes DNA replication followed by two rounds of division, resulting in four haploid cells. Each of these cells contains one complete set of chromosomes, or half of the genetic content of the original cell. If meiosis produces gametes, these cells must fuse during fertilization to create a new diploid cell, or zygote before any new growth can occur. Thus, the division mechanism of meiosis is a reciprocal process to the joining of two genomes that occurs at fertilization. Because the chromosomes of each parent undergo homologous recombination during meiosis, each gamete, and thus each zygote, will have a unique genetic blueprint encoded in its DNA. Together, meiosis and fertilization constitute sexuality in the eukaryotes, and generate genetically distinct individuals in populations. In all plants, and in many protists, meiosis results in the formation of haploid cells that can divide vegetatively without undergoing fertilization, referred to as spores. In these groups, gametes are produced by mitosis. Meiosis uses many of the same biochemical mechanisms employed during mitosis to accomplish the redistribution of chromosomes. There are several features unique to meiosis, most importantly the pairing and recombination between homologous chromosomes.
What are the main events which occur within the cell cycle?
The cell cycle is divided in two main events : interphase and mitosis. However, those two phases have further sub-divisions.InterphaseDuring interphase, the cell copies its DNA in preparation for mitosis. This phase is divided into 3 shorter phases : G1, S and G2.G1 : During this phase, the cell grows in preparation for DNA replication. Cellular components such as organelles and centrosomes are replicated.S : S is the phase where the DNA packed into chromosomes is duplicated. Replication of DNA by a certain enzyme is essential as it allows each cell created by the division to have the exact same genetic make-up. At the end of this phase, the cell contains twice its genetic material.G2 : During this phase, a certain enzyme checks and corrects any error in the duplication of the genetic material.MitosisDuring mitosis, the cell is split into two independent and identical cells. Mitosis is divided into 4 shorter phases : prophase, metaphase, anaphase and telophase.Prophase : The chromosomes start to condense and the nucleolus disappears. The nuclear envelope breaks down.Metaphase : Chromosomes align at the metaphase plate which is the centre of the cell. Anaphase : Chromatids of each chromosome are separated and start migrating towards opposite poles of the cell.Telophase : Nuclear membranes reappears, one for each set of chromosomes. Chromosomes decondense.CytokinesisCytokinesis is the division of the cytoplasm to form two cells. In the case of an animal cell, the cell is pinched in two, it is called cleavage furrow. In the case of plant cells, the cell plate forms down the middle of the cell, splitting it into two daughter cells.
What is the importance of mitosis and meiosis in the life cycle?
Mitosis is cell division: allows for growth, maturation, and replacement of damaged cells. Meiosis is the process by which gametes are made (hapliod) in order for sexual reproduction to occur.