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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.
The International System for Human Cytogenomic Nomenclature (ISCN; previously the International System for Human Cytogenetic Nomenclature) is an international standard for human chromosome nomenclature, which includes band names, symbols, and abbreviated terms used in the description of human chromosome and chromosome abnormalities.
Chromosome numbers are usually determined at the metaphase stage during mitosis. Usually, the diploid chromosome number (2n) is referenced, unless dealing with a polyploid series in which case the base number or number of chromosomes in the genome of the original haploid is quoted.
Maternally-derived chromosome rearrangement p: Short arm of a chromosome pat: Paternally-derived chromosome rearrangement psu dic: pseudo dicentric – only one centromere in a dicentric chromosome is active q: Long arm of a chromosome r: Ring chromosome t: Translocation: ter: Terminal end of arm (e.g. 2qter refers to the end of the long arm of ...
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).
The code in the "Chr.count" column specifies the total number of chromosomes in each somatic cell, and how it relates to the number n of chromosomes in each full genome set (which is also the number found in the pollen or ovule), and the number x of chromosomes in each component genome.
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child.