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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.
The basic number of chromosomes in the somatic cells of an individual or a species is called the somatic number and is designated 2n. In the germ-line (the sex cells) the chromosome number is n (humans: n = 23). [4] [5] p28 Thus, in humans 2n = 46. So, in normal diploid organisms, autosomal chromosomes are present in two copies.
A comparative chromosome map of birds' and mammals' inferred human homologies (right numbers) on chromosome idiograms [29] The third step occurred when molecular techniques were incorporated into cytogenetics. These techniques use DNA probes of diverse sizes to compare chromosomes at the DNA level.
In comparative genomics, synteny is the preserved order of genes on chromosomes of related species indicating their descent from a common ancestor.Synteny provides a framework in which the conservation of homologous genes and gene order is identified between genomes of different species. [9]
Human chromosomes, each of which contains an incomplete list of genes located on that chromosome, are as follows: Chromosome 1; Chromosome 2; Chromosome 3;
The number of pseudogenes in the human genome is on the order of 13,000, [27] and in some chromosomes is nearly the same as the number of functional protein-coding genes. Gene duplication is a major mechanism through which new genetic material is generated during molecular evolution .
All great apes have similar genetic chromosome structure. Humans have one pair fewer chromosomes than other apes, as humans have 23 chromosome pairs, while all other apes have 24, [13] with ape chromosomes 12 and 13 fused in the human genome into a large chromosome (which contains remnants of the centromere and telomeres of the ancestral 12 and ...
Schematic karyogram showing the human genome, with 23 chromosome pairs, and the human mitochondrial genome to scale at bottom left (annotated "MT"). Its genome is relatively tiny compared to the rest, and its copy number per human cell varies from 0 (erythrocytes) [1] up to 1,500,000 . [2