Terminology - SU 3

Biological sex

Sexual phenotype based on the type of gamete produced. Males are individuals that produce small gametes (often called sperm or pollen) and females are individuals that produce large gametes (often called eggs or ovules). In humans, biological sex is often based on anatomy and is frequently considered the sex assigned at birth.

Intersex

Term used to refer to an individual with a mix of typical female and male anatomical traits.

Gender

A sexual category assigned by an individual or others based on behaviour and cultural practices.

Cisgender

Individuals whose biological sex and gender are the same. For example, a cis female is one whose biological sex is female and whose gender is also female.

Transgender

Term used to describe an individual whose gender is not the same as their biological sex or their sex assigned at birth.

Gender fluid

Term used to describe an individual who feels that their gender does not easily fit into female or male categories and instead represents a mix of female and male features.

Sex determination

Specification of sex (male or female). Sex-determining mechanisms include chromosomal, genic, and environmental sex-determining systems.

Hermaphroditism

Condition in which an individual organism possesses both male and female reproductive structures. True hermaphrodites produce both male and female gametes.

Monoecious

Refers to an individual organism that has both male and female reproductive structures.

Dioecious

Belonging to a species in which an individual organism has either male or female reproductive structures.

Sex chromosome

Chromosomes that differ in number or morphology in males and females.

Autosome

Chromosome that is the same in males and females; a nonsex chromosome.

Heterogametic sex

The sex (male or female) that produces two types of gametes with respect to sex chromosomes. For example, in the XX-XY sex-determining system, the male produces both X-bearing and Y-bearing gametes.

Homogametic sex

The sex (male or female) that produces gametes that are all alike with respect to sex chromosomes. For example, in the XX-XY sex-determining system, the female produces only X-bearing gametes.

Pseudoautosomal region

Small region of the X and Y chromosomes that contains homologous gene sequences.

Genic sex determination

Sex determination in which the sexual phenotype is specified by genotypes at one or more loci, but there are no obvious differences in the chromosomes of males and females.

Sequential hermaphroditism

Phenomenon in which the sex of an individual organism changes in the course of its lifetime; the organism is male at one age or developmental stage and female at a different age or stage.

Turner syndrome

Human condition in which cells contain a single X chromosome and no Y chromosome (XO). People with Turner syndrome are female in appearance and have underdeveloped female secondary sex characteristics; most are sterile but have normal intelligence.

Klinefelter syndrome

Human condition in which cells contain one or more Y chromosomes and multiple X chromosomes (most commonly XXY but may also be XXXY, XXXXY, or XXYY). People with Klinefelter syndrome are male in appearance but frequently have small testes and reduced facial and pubic hair; they are often taller than normal and sterile, and most have normal intelligence.

Triple-X syndrome

Human condition in which cells contain three X chromosomes. A person with triple-X syndrome has a female phenotype with no distinctive features other than a tendency to be tall and thin; a few such females are sterile, but many menstruate regularly and are fertile.

Sex-determining region Y (SRY) gene

The male-determining gene in mammals, located on the Y chromosome.

Sex-linked characteristic

Characteristic determined by a gene or genes on sex chromosomes.

X-linked chracteristic

Characteristic determined by a gene or genes on the X chromosome.

Y-linked characteristic

Characteristic determined by a gene or genes on the Y chromosome.

Hemizygous

Possession of a single allele at a locus. Males of organisms with XX-XY sex determination are hemizygous for X-linked loci because their cells possess a single X chromosome.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis.

Dosage compensation

A mechanism to equalize the amount of protein produced by X-linked genes and autosomal genes. In placental mammals, dosage compensation is accomplished by the random inactivation of one X chromosome in the cells of females.

Barr body

Inactivated X chromosome that appears as a condensed, darkly staining body in the nuclei of most cells of female placental mammals.

Lyon hypothesis

Proposal by Mary Lyon in 1961 that one X chromosome in each female cell becomes inactivated (a Barr body), and that which of the X chromosomes is inactivated is random and varies from cell to cell.