Diploid chromosomes

Aspergillus nidulans diploid Chromosomal abberation - Not tested Crebelli et al. 1988... 

Rats and mice are generally used for in vivo studies, with the mouse being employed for bone marrow micronucleus analysis and the rat for metaphase analysis, but both can be used for either. Mice are cheaper and easier to handle than rats, and only a qualitative difference in response has been found between the species (Albanese et al., 1987). Chinese hamsters are also widely used for metaphase analysis because of their low diploid chromosome number of 22. However, there are few other historical toxicological data for this species. 

The diploid chromosome number is double this number except for bacteria. 

Note This information is constantly being refined, For the most current information, consult the websites for the individual genome projects, The diploid chromosome number is given for all eukaryotes except yeast,... 

This is the situation with BHK 21 hamster fibroblasts (Macpher-son and Stoker, 1962 Stoker and Macpherson, 1964) which still have the correct diploid chromosome number but which are believed to have the incorrect chromosome complement. These cells do, however, exhibit a certain amount of contact inhibition of movement ( 2.4.2) and may be further transformed by treatment with polyoma virus (e.g. to form Py Y cells Fig. 2.1) or SV40 (to form SV28 cells). 

Horikawa and Fox (1964) isolated single cells from Drosophila embryos and were able to propagate these with the diploid chromosome number for years. 

Cytology of Ammomum indicates that the diploid chromosome number of A. sub-ulatum is 48. However, variability is also reported with 2n = 26, 34, 42 and 44 (Sharma and Bhattacharya, 1959). 

The DNA that makes up our genetic material is divided into 46 pieces within the cell These pieces are called chromosomes. People have 22 numbered chromO somes, each of which occurs in duplicate, and 2 sex chromosomes. The sex chromosomes of females consist of two X chromosomes, while the sex chromosomes of males consist of one X chromosome and one Y ebtornosome. Where a cell contains duplicate copies of most, or all, of its chromosomes, the cell is called a diploid cell. Human genetic material contains an estimated 80,000 genes (Collins et aL, 1997). For comparison, the genetic material of the yeast contains 6400 genes. Not counting duplication of all DNA in the cell, which exists because of the occunence of diploid chromosomes, each human cell contains about 3 billion nucleotides in its DNA (Schuler cf ai, 1996). 

Human gametes have 23 chromosomes (haploid chromosome number n = 23), while most somatic cells have 46 chromosomes (diploid chromosome number 2n = 46). 

Jha and Jha (395) produced shoot cultures from nodal explants of seedlings. Up to 12 axillary shoots were obtained per explant using MS medium containing 0.05 ppm NAA, 8 ppm kinetin, and 200 ppm adenine. Shoot cultures could also be obtained from shoot tips on a medium containing 0.1-0.25 ppm NAA and 8 ppm kinetin. Rooting was initiated with 2 ppm IBA. The micropropagated plants all had a uniform diploid chromosome number. 

In the context of the GA, diploidy offers another method to maintain genetic diversity. The crossover operator is replaced by the fertilization operator which takes two diploid chromosomes and trades gametes, or half chromosomes (see Figure 7). A simple binary representation of the diploid chromosome uses a three-letter alphabet where a —1 implies a dominant 1, a 1 implies a recessive 1, and a 0 implies a 0. The dominance matrix is... 

With the exception of natural polyploidy in certain tissues and the absence of nuclei in eiythrocytes, the chromosome complement of the majority of somatic cells in the human body is presumed to be the initial complement—the one present in the zygote. Tissue culture cells derived from normal human donors have, in most cases, the diploid chromosome number. Strains of skin fibroblasts have been available which can be maintained in the diploid state for as long as 2 years, although a gradual decline in growth activity occurs toward the end of this period (Hayflick and Moorhead, 1961 Hayflick, 1965). In addition, cell lines with apparently normal karyotypes have been established from the peripheral leukocytes of normal individuals (Moore et aL, 1967 Glade et aL, 1968 Huang et aL, 1969 Christofinis, 1969). 

It was noted several decades ago that the early embryonic stages of several animals contain much more DNA than would correspond to a haploid, or later diploid, chromosome complement. It was suggested that most of this DNA is located within the cytoplasm. The pioneering work of Brachet and his group is especially noteworthy. The earlier results in this area have been reviewed (Brachet, 1967). At that time, the cytoplasmic DNA was believed to be associated with the yolk platelets and was assumed to be a storage form. More recent studies have established beyond doubt that most of this cytoplasmic DNA represents mt DNA. However, unequivocal identification and reliable quantitative data on mt DNA are available only for a few species such as sea urchins starfish, echiuroid worms, and frogs. 

Aneuploidy is a deviation from an exact multiple of the haploid number of chromosomes. For example, if the normal diploid chromosome number is 46 (haploid = 23), then 47 chromosomes would be an aneuploid condition. 

Chia (Salvia hispanica L.) is a member of the Laminaceae family. The center of genetic diversity of chia is in the highlands of western Mexico (Cahill, 2004), with a diploid chromosome number of 12 (Estilai et al., 1990). The genus Salvia... 

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