Sex chromatin
Sexual chromatin is divided to two kinds: X- chromatin and Y- chromatin.
X- chromatin or small body Barras is small body in form of the disk, laying on an internal surface of a nuclear membrane somatic interface cells of mammals and human. In norm X- chromatin comes to light at women, and at men is not present, because, one of X-chromosomes at women inactivates in the way of hyperspiralisation and forms small body Barra, and other X-chromosome is despiraled(despot) and in a interface nucleus is not visible. Mails have only one X-chromosome and X- chromatin is not formed. The quantity of small body Barra on one is less, than quantity of X-chromosomes, for example:
Set of sexual chromosomes |
Quantity of small body Barra |
X0, XY, XYY XX, XXY XXX, XXXY |
No 1 2 |
In norm Y- chromatin comes to light at men in nucleus of interface cells. It is luminous yellow - green small body on preparation painted quinacrine. The quantity of small body Y- chromatin is equal to quantity of Y-chromosomes.
Definition of sexual chromatin is used for cytogenetic definitions of a sex and for diagnostics of the chromosomal illnesses connected to change of quantity of sexual chromosomes.
Chromosomal illnesses
Autosomal syndromes are illnesses on the basis of change of quantity autosomal chromosomes.
Syndrome of Down is trisomy on 21-st chromosome. Frequency of a birth 1:500-700.
Karyotype 47 (21 +). Characteristic attributes: short finitenesses; a small skull; anomalies of a structure of the face; eye cracks narrow with a slanting section; epicardium (эпикант )- a pleat of upper eyelid; infringement of a structure of internal bodies; low intelligence and low immunity; a corner atd =80o; deformed, low located ears.
Syndrome Patau is trisomy on 13-th chromosome. Karyotype 47 (13 +). Frequency of a birth 1:14500. Characteristic attributes: anomalies of a structure of a mouth and a upper lip; underdevelopment or absence of eyes; the deformed ears and finitenesses; полидактилия and синдактилия (it is a lot of fingers and them joining); infringement of a structure of internal organs. They live less than one year. A corner atd =108o.
Edwards's syndrome is trisomy on 18-th chromosome. Karyotype 47 (18 +). Frequency of a birth 1:4500-6500. Characteristic attributes: a narrow forehead and a wide, acting nape; a underdeveloped, small bottom jaw; fingers of hands are wide and short; an arc pattern on fingers. They live 2-3 months.
Gonosomal syndromes are illness on the basis of change of quantity of sexual chromosomes.
Shereshevski-Turner's syndrome is monosomy on a X-chromosome. Karyotype 45 (X0). Frequency of occurrence 1:4000-5000. Characteristic attributes: underdevelopment of sexual glands; a female phenotype; wide shoulders and a narrow basin; growth of 135-145 sm; a short neck with skin pleats - «a neck of a sphynx »; a corner atd =66o; intelligence is normal; there is no small body Barra.
Syndrome of trisomy on a X-chromosome. Karyotype 47 (XXX). Frequency of occurrence 1:1000. Characteristic attributes: infringement of function ovaries; sometimes low intelligence; two small body Barra.
Syndrome of Kleinfelter. Karyotype 47 (XXY). Frequency of occurrence 1:1000. Characteristic attributes: underdevelopment of sexual glands; narrow shoulders and a wide basin; distribution of hypodermic fat as at women; the muscles are badly advanced; a man's phenotype; low intelligence; there is small body Barra.