Somatic chromosomes

Jain AK, Sarbhoy RK. 1987a. Cytogenetical studies on the effect of some chlorinated pesticides. I. Effect on somatic chromosomes of Lens and Pisum. Cytologia 52 47-54. 

A constant number of chromosomes is present in each cell. The somatic cells (i.e. not sperm or egg) are described as diploid because they contain two complete sets of chromosomes. There are 23 pairs of chromosomes in each cell, 22 pairs of somatic chromosomes (one of each pair derived from each parent) and one pair of sex chromosomes, either two Xs in the female or an X and Y in the male. Together, the 23 chromosomes contain about two metres of linear DNA or about three billion pairs of nucleotides. The linear structure of bases in DNA strands is called the primary structure of the chromosome. The secondary structure is the double heUx, in which the two complementary strands of DNA twist about each other. One turn of the helix is called a pitch and consists of ten nucleotides. 

Sarbhoy RK. 1980. Effect of para-dichlorobenzene on the somatic chromosomes and mitosis of Lens esculenta (L.) Moench. Cytologia 45 381-388. 

Grossman, A.I., Short, R.B. and Kuntz, R.E. (1981b) Somatic chromosomes of Schistosoma rodhaini, S. mattheei, and 5. intercalatum. Journal of Parasitology 67, 41-44. 

Goswami, H.K., Guron, C., Jain, N., Goswami, I. (1985). Genetic assessment of Union Carbide gas tragedy in Bhopal. I. Effects on somatic chromosomes and haemoglobin. Bionature 4 88-90. 

The human genome contains approximately 3 billion base pairs (bp) of DNA. The DNA is folded to fit within the nucleus. It is divided among chromosomes and compactly packed into chromatin by histones and other accessory proteins. Each normal somatic cell contains two copies of 22 different somatic chromosomes and two sex chromosomes (XX or XY). Less than 5% of DNA actually encodes protein and other functional products, such as tRNA, rRNA, miRNA, and other small nuclear RNAs. The majority (>95%) of human DNA consists of non-coding sequences, typically repetitive sequences such as minisatellites, microsatellites, SINEs, and LINEs. Microsatellites are short tandem repeats with each repeat unit of 1 to 13 bp long. Mini-satellites are tandemly repeated DNA sequences with the size of repeat unit of 14 to 500 bp. Microsatellite and minisatellite repeats are also known as short tandem repeats (STRs). Highly repetitive sequences containing thousands of repeated units are also found at the... 

Yadav JS, Seth N. 1998. Effect of polycyclic aromatic hydrocarbons on somatic chromosomes of coal tar workers. Cytobios 93(374) 165-173. 

Nordic Study Group on the Risk of Chromosome Damage A Nordic database on somatic chromosome damage in humans, Mutat. Res., 1990, 241, 325-337. 

Huang, H.Y., Lui, M.Y., Ladanyi, M. (2005) Nonrandom cell-cycle timing of a somatic chromosomal translocation t(X 17) of alveolar soft part sarcoma occurs in G2. Genes Chromosomes Cancer, 44, 170—176. 

HookEB. 1982. Perspectives in mutation epidemiology 2. Epidemiologic and design aspects of studies of somatic chromosome breakage and sister-chromatic exchange. Mutat Res 99 373-382. 

Ferguson-Smith, M. A., Ferguson-Smith, M. E., Ellis, P. M., and Dickson, M. (1962), The sites and relative frequencies of secondary constrictions in human somatic chromosomes. Cytogenetics 1, 325-343. 

Meiosis is specialized cell division that produces a random sampling of the normal somatic chromosome number In each spermatid. 

Some very interesting information on localization of hemoglobin loci in human somatic chromosomes has recently been obtained in two studies of the hemoglobin pattern in certain chromosomal anomalies in man (trisomy) (Huehns et al., 1964 Powars et al., 1964). 

The Drosophila embryo has provided an excellent model system for a variety of questions in chromosome biology, including investigations of somatic chromosome architecture and chromosome-associated proteins. Its advantages include the ease of obtaining populations of staged specimens (see Sisson, this volume), as well as a variety of techniques for experimental manipulation, fixation, and staining of specific cellular components. The... 

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