Symbols of chromosomes.

Karyotype of the human in norm and at chromosomal diseases demand the unified symbols of chromosomes. Now researchers of all world – clinical genetics, neuropathology’s, pediatrics, psychologists, psychiatrists use « the International system for cytogenetic nomenclatures of chromosomes of the human». According to last nomenclature such morphological attributes of chromosomes as telomeres, centromeres, specific strips on length of a chromosome, are used as comparative signs. In a chromosome allocate - short –p and long -q shoulders of chromosomes. In each shoulder allocate areas, strips and segments which are numbered from centromere to telomere, for example,record – 6 q 2,3 specifies that is a chromosome 6, a long shoulderq, area 2, a segment 3. Areas and segments on chromosomes are shown after differential coloring of chromosomes by various methodsQ, G, R, C.

In the nomenclature there is the following designations for the description normal karyotypes: 46,XX- the girl and 46,ХУ - the boy. First we write down common number of chromosomes, including sexual chromosomes. Then we write down sexual chromosomes.

Numerical anomalies are designated by change of number of chromosomes in karyotype and the indication(+) or(-) present or absentee chromosome. Exception are sexual chromosomes at which quantitative anomalies(+) or(-) are never put. Absence of one of homologues chromosomes or its part (deletion) in karyotype carries the name monosomy – full or partial, and presence – trisomy full or partial. Poliploidies are reflected only by number of chromosomes(69).

Record of autosomal genome aneuploidies:

In the beginning karyotype it is written down the common number of chromosomes, including sexual chromosomes. Then we write down sexual chromosomes. The sign plus or a minus is put before a chromosome for the indication on an additional or absentee chromosome.

There are three cytogenetic forms of a syndrome of Down: regular (simple) trisomy (93 %), translocation (5 %), mosaic (2 %). Regular trisomy a syndrome of Down in cytogenetic nomenclature enters the name as 47, XX, + 21 (girl) and 47, ХУ, +21 (boy). It is shown, that the critical segment responsible for phenotypical display of a syndrome of Down is located in a site 21q22.

Syndrome of Patau.There are three cytogenetic forms of a syndrome ofPatau: simple trisomy (75 %), translocation (20 %), mosaic (5 %), Simple trisomy of syndrome of Patau have the karyotype 47, XX, +13 (girl), 47, ХУ, +13 (boy).

Edwards's syndrome have the karyotype 47, XX, +18. Girls are born much more often.

Record of gonosom aneuploidies:

turner's syndrome – 45, Х0, (girl) full monosomy, exists a several cytogenetic variants, including mosaic forms

syndrome triplo– "X" – 47, XXX (girl) full trisomy

syndrome Kleinfelter– 47, ХХУ, (boy), exists a several cytogenetic variants

syndrome disomy on Y-chromosome 47, ХУУ (boy).

Structural anomalies of chromosomes - deletions, duplications, inversions, and translocation designate as: del (-), dup (+), inv, and t accordingly, robertson translocation - rob. When it is necessary to designatea certainsite at the description of anomalies of chromosomes in the beginning write number of chromosomes in karyotype, then number of a chromosome in which there was a mutation, then a symbol of a shoulder (p or q) and signs plus or a minus is written down after a symbol of a shoulder. 46, XX, del, X p – female karyotype with 46 chromosomes and deletion a long shoulder X – chromosomes. 45, XX, rob 15,16 – karyotype with 45 chromosomes and robertson translocation, 46, ХУ, t 2,5, q21, q31 – translocation has taken place between segments of 21 and 31 long shoulders of 2 and 5 chromosomes.

Record autosomal aberrations:

Syndrome of Volf- Hirshhorn – partial monosomy, deletion (loss of a part of a genetic material) of a short shoulder of 4 chromosomes 46,4 p–, ХУ, loss of a segment p 16

Syndrome of " shout of a cat » - partial monosomy, deletion of a short shoulder of 5 chromosomes, 46, 5p–, XX, loss of a segment p 15, mosaic forms are described

Philadelphia chromosome Ph – deletion 21 chromosomes. It comes to light only in cells of hemopoietic systems (a bone brain, granulocytes). The mutant cells supersede normal hemopoietic cells. At carriers of this mutation develops chronic myeloleukemia.

Translocation robertson (rob) forms:

syndrome of Down – 46, t 21/21, XX; 46, t 21/15, ХУ ;

syndrome Patau– 46, t 13/13, XX; 46, t 13/15, ХУ.