Chromosomes karyotyping

Adrenal angiography Adrenal venography Adrenocorticotropic hormone stimulation test Aldosterone assay, blood Androstenedione Antidiuretic hormone Antithyroglobulin antibody Antithyroid microsomal antibody Blood glucose Calcitonin Calcium Catecholamines Chromosome karyotype Computed tomography of adrenals Cortisol blood urine C-peptide... 

Fig. 2. Karyotype of 10 S. cerevisiae strains. Intact chromosomes have been separated electrophoreticaUy by size in a TAPE gel. (a), gel mn to separate most chromosomes. Large chromosomes are at the top, smaller at the bottom. Since most strains are polyploid, more than 16 bands may be observed, (b). Chromosomes from the same strains have been separated in a gel mn to enhance resolution of the smaller chromosomes, corresponding to the 4—5...

Figure 36-6. A human karyotype (of a man with a normal 46,XY constitution), in which the metaphase chromosomes have been stained by the Giemsa method and aligned according to the Paris Convention. (Courtesy of H Lawce and F Conte.)...

Cytogenetic Analysis and Sex Determination. Since amnlotlc fluid cells are fetal In origin, they have the chromosome complement of the fetus Itself Therefore, the chromosomes of the fetus can be examined by karyotyping the cultured amnlotlc fluid cells There are two principal reasons for examining fetal chromosomes One, the numerically less frequent reason. 

While all chromosomal abnormalities can In principle be detected by prenatal diagnosis, fetal karyotyping Is not at present being done as a general screening procedure Rather,... 

Karyotypic Number, size, and structure of cell chromosomes. 

Nadzhafova, R.S., N.S. Bulatova, A.I. Kozlovskii, and I.N. Ryabov. 1994. Identification of a structural chromosomal rearrangement in the karyotype of a root vole from Chernobyl. Russian Jour Genet. 30 318-322... 

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). 

This picture of the human chromosomes lined up in pairs is called a karyotype. 

Karyotype The characteristic chromosome complement of an individual, race, or species as defined by their number, size, shape, etc. [NIH]... 

Another important feature of the transformed/immortalized cells is their karyotype. While in the early stages of transformation, most of the cells will retain a near diploid karyotype. However, once the cells have gone through a crisis event or are growing well beyond the typical crisis period (— 15—30 subcultures), they are aneuploid with a characteristic distribution of individual chromosomes, that is, there are likely to be multiple copies of specific chromosomes while others are not cytogenetically detectable. 

Kazmierczak, B., B. Thode, S. Bartnitzke, J. Bullerdiek, and W. Schloot. 1992. Pleomorphic adenoma cells vary in their susceptibility to SV40 transformation depending on the initial karyotype. Genes Chromosomes Cancer 5(1) 35-9. 

During mitosis, aU the DNA is highly condensed to allow separation of the sister chromatids. This is the only time in the ceE cycle when the chromosome structure is visible. Chromosome abnormalities may be assessed on mitotic chromosomes by karyotype analysis (metaphase chromosomes) and by banding techniques (prophase or prometaphase), which identify aneu-ploidy, translocations, deletions, inversions, and duplications. 

A normal male karyotype is labeled 46,XY (46 chromosomes, including one X and one Y). Similarly, a normal female karyotype is labeled 46,XX. A complex nomenclature has been devised to describe deviations from these karyotypes. This nomenclature is given in Table II-3-1. 

Klinefelter syndrome (47,XXY) is seen in approximately 1 in 1,000 males (all individuals with this condition have a male phenotype because they have a Y chromosome). Klinefelter males are nearly always sterile because of atrophy of the seminiferous tubules. They tend to be taller than average, with abnormally long arms and legs. Breast development (gynecomastia) is seen in about one third of cases, and the IQ is on average 10-15 points below that of unaffected siblings. Individuals have also been seen with 48.XXXY and 49,XXXXY karyotypes the additional X chromosomes produce a more severely affected phenotype. 

Other common, but less clinically significant, sex chromosome aneuploidies are the 47,XXX (1/1,000 females) and 47,XYY (1/1,000 males) karyotypes. The former karyotype is associated with increased stature and a mild decrease in IQ, and the latter is associated with increased stature, mild decrease in IQ, acne, and a susceptibility to impulsive behavior (early studies suggesting a propensity to violent criminal behavior have not been substantiated). 

The cri-dii-chat syndrome, which is the result of a terminal deletion of the short arm of chromosome 5 (karyotype 4 ,XY,del[5p]), is a classic example of a chromosome deletion. The name is derived from the French term "cry of the cat," which denotes the characteristic kittenlike cry of babies with this condition. It is rare, affecting approximately 1 in 50,000 newborns. Characteristic features include mental retardation (average IQ of 35), miaocephaly, and wide-set eyes. Most children born with this condition do not survive to adulthood. 

A ring chromosome can form when a deletion occurs on both tips of a chromosome and the remaining chromosome ends fuse together (the karyotype for a female with a ring chromosome X would be 46, r[X]). Ring chromosomes are often lost, resulting in a monosomy (e.g., loss of a ring X chromosome would produce Turner syndrome). They have been observed at least once for each human chromosome. 

Spectral karyotyping involves the use of five different fluorescent probes that hybridize differentially to different sets of chromosomes. In combination with special cameras and image-pro-cessing software, this technique produces a karyotype in which every chromosome is painted a different color. This aDows the ready visualization of chromosome rearrangements such as small translocations (e.g., the Philadelphia chromosome rearrangement discussed above). 

A karyotype of the child s chromosomes (choice C) might reveal X chromosomes with the decondensed long arm characteristic of this syndrome, but not all X chromosomes have this appearance in affected individuals. Thus, the karyotype may yield a false-negative diagnosis. 

Hashimoto, K. (1992) Flow karyotyping and chromosome sorting. Nippon Rinsho. 50,2484-2488. 

Milan, D., Yerle, M., Schmitz, A., Chaput, B., Vaiman, M., Frelat, G., and Gellin, J. (1993) A PCR-based method to amplify DNA with random primers determining the chromosomal content of porcine flow-karyotype peaks by chromosome painting. Cytogenet. Cell Genet. 62,139-141. 

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