Chromosome number

Table 2.20 Sesquiterpenes, chromosome numbers, and flower head features for Ambrosia camphorata (after Seaman and Mabry, 1979a)...

We are concerned here with systems that have been studied using secondary products—flavonoids and terpenoids in particular— but other information, including micro- and macrofossils, and occasionally chromosome numbers, will be included in the discussions when snch information is available. The majority of current research on postglacial reestablishment of plant distribution patterns is based on DNA seqnence information. In a few instances below, reference will be made to such information, but this in not the place for a detailed review of that literature. 

The DNA content of blast cells, hyper-, hypo-, or diploid, corresponding to increased, decreased, or normal chromosome numbers, has been considered prognostic. Lower-risk patients with hyperdiploidy (greater than 50 chromosomes) generally are between the ages of 1 and 9 years, whereas the higher-risk patients with normal diploidy (50 chromosomes) generally are older. 

In 1993/1994 a series of publications caused a stir in the AD research community, since for the first time they linked a specific neuropathological process in late-onset AD to a genetic marker. Researchers looking at the composition of plaques found that the protein apolipoprotein E (ApoE) was associated with p-amyloid in the cerebrospinal fluid (CSF) of AD patients (Strittmatter et al., 1993). The gene for ApoE is on the same human chromosome (number 19) which was a risk factor in some AD pedigrees. The gene for ApoE comes in three versions (alleles) Apo s2, Apo s3 and, most importantly, Apo s4 these result in three slightly different variants of the protein. Humans carry two versions of the allele and so can have none, one or two of any of the versions of the Apo... 

HSA is a 585 amino acid, 65.5 kDa polypeptide. It is one of the few plasma proteins that are unglycosylated. A prominent feature is the presence of 17 disulfide bonds, which help stabilize the molecule s three-dimensional structure. HSA is synthesized and secreted from the liver, and its gene is present on human chromosome number 4. 

Chromosome defects arise at the level of the individual chromosome or at the level of the chromosomal set, so affecting chromosomal number in subsequent cell replications. 

The TK+/ fine was originally isolated as a spontaneously arising revertant clone from a UV-induced TK / clone. The parental TK+/+ cell and the heterozygote were then the only TK-competent mouse lymphoma cells that could be maintained in THMG medium (3 pg ml-1 thymidine, 5 pg ml-1 hypoxanthine, 0.1 pg ml-1 methotrexate and 7.5 pg ml-1 glycine) (Clive, 1987). Thus, like most established lines, these cells are remote from wild-type cells. The karyotype of the TK+/ —3.7.2C line has a modal chromosome number of 40 like wild-type, but has a variety of chromosomal rearrangements and centromeric heteromorphisms (Blazak et al., 1986). 

Chinese hamster ovary cells in which there has been an extensive rearrangement of chromosome material and the chromosome number may not be constant from cell to cell, are frequently used. Polyploidy, endoreduplication and high spontaneous chromosome aberration frequencies can sometimes be found in these established cell lines, but careful cell culture techniques should minimize such effects. Cells should be treated in exponential growth when cells are in all stages of the cell cycle. 

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 chromosome on which the gene can be found. The first number or letter used to describe a gene s location represents the chromosome. Chromosomes 1 through 22 (the autosomes) are designated by their chromosome number. The sex chromosomes are designated by X or Y. 

The other type of cell division, meiosis, ensures that humans have the same number of chromosomes in each generation. It is a two-step process that reduces the chromosome number by half—from 46 to 23—to form sperm and egg cells. When the sperm and egg cells unite at conception, each contributes 23 chromosomes so the resulting embryo will have the usual 46. Meiosis also allows genetic variation through a process of DNA shuffling while the cells are dividing. 

Many cancer cells also have changes in their chromosome number or structure. These changes most often occur in somatic cells (cells other than eggs and sperm) during a person s lifetime. 

Within the cell is the nucleus with the chromosomes. DNA strands are housed within the chromosomes, together with some proteins. The 46 human chromosomes are grouped into 22 pairs and two sex chromosomes. Numbering of chromosomes is based on size, chromosome 1 being the largest and 22 the smallest. 

Ota T, Suto S, Katayama H, Han ZB, Suzuki F, Maeda M, Tanino M, Terada Y, Tatsuka M (2002) Increased mitotic phosphorylation of histone H3 attributable to AIM-l/Aurora-B overexpression contributes to chromosome number instability. Cancer Res 62(18) 5168-5177 Paulson JR, Taylor SS (1982) Phosphorylation of histones 1 and 3 and nonhistone high mobihty group 14 by an endogenous kinase in HeLa metaphase chromosomes. J Biol Chem 257(11) 6064—6072 Petersen J, Paris J, Wilier M, Philippe M, Hagan IM (2001) The S. pombe aurora-related kinase Arkl associates with mitotic structures in a stage dependent manner and is required for chromosome segregation. J Cell Sci 114(Pt 24) 4371 384... 

Diseases can be caused by abnormalities in chromosome number or structure Numerical chromosome abnormalities Euploidy (multiple of 23 chromosomes) ... 

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). 

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

Mitotic effect. STE, administered to the buccal mucosa of 15 female HMT rats, 6 months of age, weekly for 1 year, produced hyperorthokeratosis, acanthosis, numerous binucleate spinous cells, and subepithelial connective tissue hyalinization. Verrucous carcinoma and squamous cell carcinoma were not seen. Karyotyping revealed that lymphocytes of tobacco-treated, as well as control rats, had normal chromosome number and morphology. However, approx 25% of buccal epithelial cells of the tobacco-treated rats were tetraploid and 5% octa-ploid, compared with only 11% tetraploid and no octaploid in the controls. Results indicated that the mitotic process could be disturbed by tobacco treatment b Molluscicidal activity. Water extract of the dried leaf, at a concentration of 168 ppm, produced equivocal effect on Lymnaea luteola . 

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