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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 .
Polyploidy in animals is much less common, but it has been significant in some groups. [43] Polyploid series in related species which consist entirely of multiples of a single basic number are known as euploid. Haplo-diploidy, where one sex is diploid, and the other haploid. It is a common arrangement in the Hymenoptera, and in some other groups.
A haplotype is a group of alleles in an organism that are inherited together from a single parent, [1] [2] and a haplogroup (haploid from the Greek: ἁπλοῦς, haploûs, "onefold, simple" and English: group) is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism mutation. [3]
A seemingly logical consequence of descent from common ancestors is that more closely related species should have more chromosomes in common. However, it is now widely thought that species may have phenetically similar karyotypes due to genomic conservation. Therefore, in comparative cytogenetics, phylogenetic relationships should be determined ...
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]
The following articles are lists of human Y-chromosome DNA haplogroups found in populations around the world. Y-DNA haplogroups by ethnic group; Y-DNA haplogroups in populations of Europe; Y-DNA haplogroups in populations of the Caucasus; Y-DNA haplogroups in populations of the Near East; Y-DNA haplogroups in populations of North Africa
In 1973, M. J. D. White, then at the end of a long career investigating karyotypes, gave an interesting summary of the distribution of chromosome polymorphism. "It is extremely difficult to get an adequate idea as to what fraction of the species of eukaryote organisms actually are polymorphic for structural rearrangements of the chromosomes.
The human genome has been sequenced, as well as the chimpanzee genome. Humans have 23 pairs of chromosomes, while chimpanzees, gorillas and orangutans have 24. Human chromosome 2 is a fusion of two chromosomes 2a and 2b that remained separate in the other primates. [9]