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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.
Euploidy and aneuploidy describe having a number of chromosomes that is an exact multiple of the number of chromosomes in a normal gamete; and having any other number, respectively. For example, a person with Turner syndrome may be missing one sex chromosome (X or Y), resulting in a (45,X) karyotype instead of the usual (46,XX) or (46,XY).
Hybridization without change in chromosome number is called homoploid hybrid speciation. It is considered very rare but has been shown in Heliconius butterflies [83] and sunflowers. Polyploid speciation, which involves changes in chromosome number, is a more common phenomenon, especially in plant species. [citation needed]
Having multiple sets of chromosomes is called polyploidy. Polyploidy is usually fatal in animals where extra chromosome sets upset fetal development, but is often found in plants. [17] A form of hybrid speciation that is relatively common in plants occurs when an infertile hybrid becomes fertile after doubling of the chromosome number.
Most species whose cells have nuclei are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid. Polyploidy is especially common in plants.
Artificial chromosomes are manufactured chromosomes in the context of yeast artificial chromosomes (YACs), bacterial artificial chromosomes (BACs), or human artificial chromosomes (HACs). An artificial chromosome can carry a much larger DNA fragment than other vectors. [9] YACs and BACs can carry a DNA fragment up to 300,000 nucleotides long.
The proposal to change the names of roughly 150 bird species from across North America is ruffling feathers among ornithologists and other bird lovers as a simmering debate grows increasingly heated.
The small pieces are then assembled into contigs by overlapping them. Next, using the map from the first step the contigs are assembled back into the chromosomes. The first complete plant genome assembly (also the first plant genome published) that used this type of technique was Arabidopsis thaliana, in 2000. [12]