Ch. 4 Sex Determination and Sex-Linked Characteristics Flashcards
(24 cards)
sex
sexual phenotype: male or female
sex determination
specification of sex (male or female); sex-determining mechanisms include chromosomal, genie, 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 whose individual members have 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
homogametic sex
the sex (male or female) that produces gametes that are all alike with regard to sex chromosomes
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 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 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); people 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
triple-X syndrome
human condition in which cells contain three X-chromosomes; 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 (SRY) gene
gene on the Y chromosome that triggers male development
sex-linked characteristic
characteristic determined by a gene or genes on sex chromosomes
X-linked characteristic
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
hemizygosity
possession of a single allele at a locus; males of organisms with XX-XY sex determination are homozygous 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
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 chromosome in the cells of females
Barr body
inactivated X chromosome that appears as a condensed, darkly staining structure in 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
