Diploid number

All nucleated cells except eggs and sperm (gametes) carry two sets of genetic material in their nuclei, one from the individual s mother and one from the father, hi human cells there are 22 pairs of homologous chromosomes plus an X chromosome and a Y chromosome. In the formation of gametes, this must be reduced to a single set, that is, the diploid number of chromosomes (46) must be reduced to the haploid number (23). 

Positive results in the mammalian in vivo bone marrow chromosome aberration test indicate that a substance induces stmctural chromosome aberrations in the bone marrow of the species tested. An increase in polyploidy (a multiple of the haploid chromosome number (n) other than the diploid number, i.e., 3n, 4n and so on) may indicate that a substance has the potential to induce numerical aberrations (change in the number of chromosomes from the normal number characteristic of the animals utilized). 

Fertilization The fusion of the sperm and ovum resulting in the restoration of the diploid number of chromosomes. 

SOMATIC CELL One of the two cell types (the other being a germ cell) of a multicellular diploid organism it contains a diploid number of chromosomes and is involved in all functions of the organism except fertilization. 

The chromosomes constitution of cells, or cell hybrids, is an important criterion for monitoring the nature of cells in culture. It may help to indicate contamination of the cells of one species with those of another and enables the elucidation of the chromosomal location of various genetic markers. In vitro, however, cells often change their chromosome constitution and most cell lines no longer have the diploid number of chromosomes. Rather they are aneuploid and may have a wide range of chromosomes per cell (see 2.2)... 

Human somatic cells contain 46 chromosomes, cattle 60. and fruit fly 8. Thus, the diploid number bears no relationship to the species positions in the phylogenetic scheme of classification. 

A cell with a diploid number of 24 undergoes meiosis, how many... 

Heteroploid The term given to a cell culture when the cells comprising the culture possess nuclei containing chromosome numbers other than the diploid number. This is a term used only to describe a culture and is not used to describe individual cells. Thus, a heteroploid culture would be one that contains aneuploid cells. 

In vertebrates and diploid yeasts, cells in Gi have a diploid number of chromosomes (2/i), one inherited from each parent. In haploid yeasts, cells In Gi have one of each chromosome (l/i), the haploid number. Rapidly replicating human cells progress through the full cell cycle In about 24 hours mitosis takes —30 minutes Gi, 9 hours the S phase, lO hours and G2, 4.5 hours. In contrast, the full cycle takes only —90 minutes In rapidly growing yeast cells. 

Hemp breeders have long known that Cannabis strains can easily be crossed with each other. What they don t know is the relative fertility of the second generations. Researchers recently crossed 38 strains representing each of the tive cannabinoid types and found that all of the hybrids had the normal diploid number of chromosomes (2n = 20), normal meiosis (division of the chromosomes during sexual reproduction), completely strainable pollen (a criterion for fertility), and no chromosomal aberrations. The hybrids were also exceptionally vigorous (a frequent observation when crossing strains of plants) and so there are apparently no breeding barriers between different populations. However, the definitive test of the fertility of the hybrids will be their ability to produce fertile seeds, and all populations have not been tested for interfertility. 

Chromosome number. In animals, each somatic cell (body cells excluding sex cells) contains one set of chromosomes inherited from the female parent and a comparable (homologous) set from the male parent. The number of cbromosomes in the dual set is called the diploid number, the suffixploid means a set, and di refers to the multiplicity of the set. Sex cells (called gametes) contain one-half the number of chromosomes of somatic cells and are therefore referred to as haploid cells. A genome is the set of chromosomes that corresponds to the haploid set of a species. 

Meiosis Reduction division where the diploid number of chromosomes is... 

The number of unique chromosomes is called the haploid number (N), but there are two copies of each, and 2N is called the diploid number. 

S. Pathak, O. G. Ward and T. C. Hsu, Rate of sister chromatid exchanges in mammalian cells differing in diploid numbers, Expenentia 33, 875-876 (1977). 

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