Genetics

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18 Cards. Created by Alizabeth ().
Chapter 4
 
Term  
Definition

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.

Monoecious Organism

Individual Organism that has both male and female reproductive structures

Dioecious Organism

Belongs to a species whose members have either male or female reproductive structures.

Sex Chromosomes

Chromosomes that differ morphologically or in number in male and females.

Autosome

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

Homogametic Sex

The sex (male or female) that produces gametes that are all alike with regard 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 genes at one or more loci, but there are no obvious differences in the chromosomes of males and females.

Genic Balance System

Sex-determining system in which sexual phenotype is controlled by a balance between genes on the X chromosome and genes on the autosomes.

Turner Syndrome

Human condition in which cells contain a single X chromosome and no Y chromosome (XO). Persons with Turner syndrome are female in appearance but do not undergo puberty and have poorly developed female secondary sex characteristics; most are sterile but have normal intelligence.

Klinefelter Syndrome

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

Triplo-X Syndrome

Human condition in which cells contain 3 X chromosomes. A person with triple-X syndrome has female phenotype without distinctive features other than a tendency to be tall and thin; a few such women are sterile, but many menstruate regularly and are fertile.

Sex-determining Region Y (SRY) Gene

On the Y chromosome, a gene that triggers male development.

Sex-LInked characteristic

Characteristic determined by a gene or genes on sex chromosomes.

Hemizygosity

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

Nondisjunction

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

Dosage Compensation

Equalization in males and females of the amount of protein produced by X-linked genes. In placental mammals, dosage compensation is accomplished by the random inactivation of one X chromosomes in the cells of females.

Barr Body

Condensed, darkly staining structure that is found in most cells of female placental mammals and is an inactivated X chromosome.