sex chromatin

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chromatin

 [kro´mah-tin]
the substance of the chromosomes, composed of DNA and basic proteins (histones), the material in the nucleus that stains with basic dyes.
sex chromatin the persistent mass of the material of the inactivated X chromosome in cells of normal females; called also Barr body.

sex chro·ma·tin

a small condensed mass of the inactivated X-chromosome usually located just inside the nuclear membrane of the interphase nucleus; the number of sex chromatin bodies per nucleus is one less than the number of X-chromosomes; normal males and females with Turner syndrome (XO) have none (sex chromatin negative), normal females and males with Klinefelter syndrome (XXY) have one, and XXX-females have two. For technical reasons only about half the cells in a preparation show typical masses.
See also: Lyon hypothesis.
Synonym(s): Barr chromatin body

sex chromatin

n.

sex chromatin

a densely staining mass within the nucleus of all nondividing cells of normal mammalian females. It represents the heterochromatin of the inactivated X chromosome. Examination of cells obtained by amniocentesis for the presence of sex chromatin is a technique used for determining the sex of a baby before birth. Sex chromatin is also found as a drumstick-shaped mass attached to one of the nuclear lobes in polymorphonuclear leukocytes in normal females. Also called Barr body. See also Lyon hypothesis.

Barr body

A condensed clump of chromatin that corresponds to an inactivated X chromosome, which is located next to the nuclear membrane, and best seen in somatic cells in interphase. The number of BBs per cell is 1 less than the number of X chromosomes, thus normal XX women cells will have one BB, as do men with 47 XXY (Klinefelter syndrome). Normal XY males have none, nor do 45 XO (Turner syndrome) females.

sex chro·ma·tin

(seks krō'mă-tin)
A small, condensed mass of the inactivated X-chromosome usually located just inside the nuclear membrane of the interphase nucleus; the number of sex chromatin bodies per nucleus is one less than the number of X-chromosomes; hence, normal males have none and normal females have one. For technical reasons, only about half the cells in a preparation show typical masses.
See also: Lyon hypothesis
Synonym(s): Barr chromatin body.

sex chromatin

see BARR BODY.

Barr,

Murray Liewellyn, Canadian microanatomist, 1908–.
Barr body - Synonym(s): Barr chromatin body
Barr chromatin body - a small condensed mass of the inactivated X-chromosome usually located just inside the nuclear membrane of the interphase nucleus. Synonym(s): Barr body; sex chromatin

chromatin

the substance of the chromosomes, composed of nucleic acids and basic proteins (histones), the material in the nucleus that stains with basic dyes.

sex chromatin
Barr body; the persistent mass of the material of the inactivated X chromosome in cells of normal females. See also drumstick.

sex

1. the fundamental distinction, found in most species of animals and plants, based on the type of gametes produced by the individual or the category to which the individual fits on the basis of that criterion. Ova, or macrogametes, are produced by the female, and spermatozoa, or microgametes, are produced by the male. The union of these distinctive germ cells results in the production of a new individual in sexual reproduction.
2. to determine the sex of an animal.

sex cell
see germ cell, gamete.
sex chromatin
the persistent mass of chromatin situated at the periphery of the nucleus in cells of normal females; it is the material of the inactivated sex chromosome. Called also Barr body.
chromosomal sex
sex as determined by the presence of the XX (female) or the XY (male) genotype in somatic cells, without regard to phenotypic manifestations. Called also genetic sex.
sex chromosomes
see sex chromosomes.
sex determination
1. the change in the fetus to a male or female configuration; the process by which the sex of an organism is fixed, associated, in animals, with the presence or absence of the Y chromosome.
2. diagnosis of the sex of the fetus before birth performed by examination of fetal fluids obtained by amniocentesis.
sex determining region of Y
a single gene responsible for determining the sex of an animal.
sex drive
see libido.
endocrinological sex
the phenotypic manifestations of sex determined by endocrine influences, such as mammary development, etc.
genetic sex
chromosomal sex.
sex glands
in the male includes the prostate, seminal vesicles, ampullae and bulbourethral glands; in the female includes ovaries.
gonadal sex
the sex as determined on the basis of the gonadal tissue present (ovarian or testicular).
sex hormones
glandular secretions involved in the regulation of sexual functions. The principal sex hormone in the male is testosterone, produced by the testes. In the female the principal sex hormones are the estrogens and progesterone, produced by the ovaries.
These hormones influence the secondary sex characters, such as the shape and contour of the body and head, mammary development and the pitch of the voice. The male hormones stimulate production of spermatozoa, and the female hormones control ovulation, pregnancy and the estral cycle.
sex-linkage
includes X-linked (much the most common) and Y-linked loci.
sex-linked inheritance
see sex-linkage (above).
morphological sex
sex determined on the basis of the morphology of the external genitals.
neutrophil sex lobe
see drumstick lobe.
nuclear sex
the sex as determined on the basis of the presence or absence of sex chromatin in somatic cells, its presence normally indicating the XX (female) genotype, and its absence the XY (male) genotype.
sex parity
see sex ratio (below).
sex pheromone
sex ratio
proportion of female to male births.
sex reversal
the sexual condition of animals in which gonadal sex and chromosomal sex are dissimilar.
sex steroids
steroidal compounds acting as hormones in reproductive processes; the principal ones are estrogen, progesterone, testosterone.