sex chromatin
Học thuậtThân thiện
Definition
Noun 1. A mass of chromatin found only in female cells: A distinct, condensed structure of chromatin (DNA and protein) that is observable in the nucleus of cells from individuals with two X chromosomes. It represents one of the two X chromosomes that is largely inactivated.
Usage
- Sex chromatin is a biological marker used to identify genetic sex at a cellular level.
- The standard test involves examining cells, often from a buccal (cheek) smear, for the presence of this structure.
- Its presence typically indicates a female genotype (XX), while its absence typically indicates a male genotype (XY).
Examples
- The presence of sex chromatin in the cell's nucleus confirmed the sample was from a female.
- Sex chromatin analysis was a common method for sex determination before more advanced genetic techniques were developed.
- The absence of sex chromatin in the amniotic fluid cells suggested the fetus was male.
Advanced Usage
- Barr body: This is a direct synonym for sex chromatin, named after the scientist Murray Barr who discovered it. The terms are often used interchangeably in genetics and cytology.
- The report noted the presence of a Barr body, or sex chromatin, in the sampled cells.
Variants and Related Words
- Barr body (n): A synonym for sex chromatin.
- X-chromatin (n): Another less common term emphasizing its origin from an X chromosome.
- Lyonization (n): The process of X-chromosome inactivation, which creates the sex chromatin/Barr body.
Synonyms
- Barr body
Notes on Meaning
The term sex chromatin refers specifically to the inactivated X chromosome visible as a dense body. It is not a general term for all chromatin related to sex chromosomes. Its primary utility is as a diagnostic cytogenetic marker.
Noun
- chromatin found only in female cells
- the presence or absence of sex chromatin in cells obtained by amniocentesis makes it possible to determine the sex of a fetus