Search results
Results from the WOW.Com Content Network
However, some organisms are polyploid. Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid.
Zygoidy is the state in which the chromosomes are paired and can undergo meiosis. The zygoid state of a species may be diploid or polyploid. [51] [52] In the azygoid state the chromosomes are unpaired. It may be the natural state of some asexual species or may occur after meiosis. In diploid organisms the azygoid state is monoploid.
There are many ways in which a polyploid organism can convert back to a diploid status. This is usually achieved by elimination of duplicated genes. The main goals of diploidization are: (1) To ensure proper gene dosage; and (2) to maintain stable cellular division processes.
Macronuclei and micronuclei differ in their functions even though they are located within the same cell. The micronucleus is globally repressed during the vegetative state, and serves as the diploid germline nucleus, whereas all known vegetative gene expression happens in the macronucleus, which is a polyploid somatic nucleus. [3]
Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote.. Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
Triploid bridges occur in low frequencies in populations and are produced when unreduced gametes combine with haploid (1N) gametes to produce a triploid offspring that can function as a bridge to the formation of tetraploids. [36] In both paths, the polyploid hybrids are reproductively isolated from the parents due to the difference in ploidy.
Allopolyploid species - a polyploid hybrid species where the two chromosome sets are derived from different parent species. Backcrossing - crossing of a hybrid with one of its parent species. Extrinsic incompatibilities - Environment-dependent reproductive barrier. For example, when trait combinations lead to reduced fitness in the hybrid ...