Search results
Results From The WOW.Com Content Network
The term 'chromosome' is sometimes used in a wider sense to refer to the individualized portions of chromatin in cells, which may or may not be visible under light microscopy. In a narrower sense, 'chromosome' can be used to refer to the individualized portions of chromatin during cell division, which are visible under light microscopy due to ...
An illustration of interphase. The chromatin has not yet condensed, and the cell is undergoing its normal functions. An image of the nucleus of a cell currently in interphase (likely G1). Note: Cytoplasm of this cell or the neighboring cell is not visible (top-left), which is currently in the telophase of mitosis.
Aneuploidy is the condition in which the chromosome number in the cells is not the typical number for the species. This would give rise to a chromosome abnormality such as an extra chromosome or one or more chromosomes lost. Abnormalities in chromosome number usually cause a defect in development. Down syndrome and Turner syndrome are examples ...
It is, however, not well-characterised. Chromosome scaffolds play an important role to hold the chromatin into compact chromosomes. Loops of 30 nm structure further condense with scaffold, into higher order structures. [21] Chromosome scaffolds are made of proteins including condensin, type IIA topoisomerase and kinesin family member 4 (KIF4). [22]
The identical sister chromatids have not yet condensed into the densely packaged chromosomes visible with the light microscope. This will take place during prophase I in meiosis. Growth 2 (G 2 ) phase : G 2 phase as seen before mitosis is not present in meiosis.
Points of crossing over become visible as chiasma after the synaptonemal complex dissembles and the homologous chromosomes slightly apart from each other. The phenomenon of genetic chiasmata (chiasmatypie) was discovered and described in 1909 by Frans Alfons Janssens, a Professor at the University of Leuven in Belgium. [3] [4]
An extra or missing chromosome is a common cause of some genetic disorders. Some cancer cells also have abnormal numbers of chromosomes. [3] [4] About 68% of human solid tumors are aneuploid. [4] Aneuploidy originates during cell division when the chromosomes do not separate properly between the two cells (nondisjunction).
The thick lines are chromosomes, and the thin blue lines are fibers pulling on the chromosomes and pushing the ends of the cell apart. The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3. Cell division is the process by which a parent cell divides into two daughter cells. [1]