Cytomixis
Encyclopedia
Cytomixis is a process of chromosome
transfer that can occur during pollen
formation in flowering plants. It results in pollen grains with chromosome numbers greater or less than the haploid number, possibly including some that are diploid or polyploid, and often producing some non-viable pollen grains.
During cytomixis "there is, at least in some flowers but probably not in all, an extrusion of chromatin
from the nucleus
of one [pollen-]mother-cell through cytoplasmic connections, into the cytoplasm of an adjacent mother-cell." Cells may also fuse completely.
The phenomenon appears to have a genetic component.
Diploid or polyploid pollen grains produced by cytomixis may have a significant role in evolution.
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
transfer that can occur during pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
formation in flowering plants. It results in pollen grains with chromosome numbers greater or less than the haploid number, possibly including some that are diploid or polyploid, and often producing some non-viable pollen grains.
During cytomixis "there is, at least in some flowers but probably not in all, an extrusion of chromatin
Chromatin
Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...
from the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
of one [pollen-]mother-cell through cytoplasmic connections, into the cytoplasm of an adjacent mother-cell." Cells may also fuse completely.
The phenomenon appears to have a genetic component.
Diploid or polyploid pollen grains produced by cytomixis may have a significant role in evolution.
See also
- ApomixisApomixisIn botany, apomixis was defined by Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. This definition notably does not mention meiosis...
in flowering plants: various processes that occur in the gynoeciumGynoeciumGynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
, some of which involve doubling the chromosome number. - ParthenogenesisParthenogenesisParthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
, the animalAnimalAnimals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
equivalent of apomixis.