Search results
Results from the WOW.Com Content Network
The mitosis process in the cells of eukaryotic organisms follows a similar pattern, but with variations in three main details. "Closed" and "open" mitosis can be distinguished on the basis of nuclear envelope remaining intact or breaking down. An intermediate form with partial degradation of the nuclear envelope is called "semiopen" mitosis.
Mitotic cell division enables sexually reproducing organisms to develop from the one-celled zygote, which itself is produced by fusion of two gametes, each having been produced by meiotic cell division. [5] [6] After growth from the zygote to the adult, cell division by mitosis allows for continual construction and repair of the organism. [7]
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms. Prokaryotic cells divide by binary fission , while eukaryotic cells usually undergo a process of nuclear division, called mitosis , followed by division of the cell, called cytokinesis .
During mitosis, which is also known as the M-phase, the segregation of the chromosomes occur. [36] DNA, like every other molecule, is capable of undergoing a wide range of chemical reactions. Modifications in DNA's sequence, on the other hand, have a considerably bigger impact than modifications in other cellular constituents like RNAs or ...
The cell on the left is going through mitosis and its DNA has condensed. In biology , cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of cells , that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells.
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete (haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes . [1]
All living organisms are the products of repeated rounds of cell growth and division. [5] During this process, known as the cell cycle, a cell duplicates its contents and then divides in two. The purpose of the cell cycle is to accurately duplicate each organism's DNA and then divide the cell and its contents evenly between the two resulting cells.