Ch. 4 Sex Determination and Sex-Linked Characteristics

Question 1

sex

Answer 1

sexual phenotype: male or female

Question 2

sex determination

Answer 2

specification of sex (male or female); sex-determining mechanisms include chromosomal, genie, and environmental sex-determining systems

Question 3

hermaphroditism

Answer 3

condition in which an individual organism possesses both male and female reproductive structures; true hermaphrodites produce both male and female gametes

Question 4

monoecious

Answer 4

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

Question 5

dioecious

Answer 5

belonging to a species whose individual members have either male or female reproductive structures

Question 6

sex chromosome

Answer 6

chromosomes that differ in number or morphology in males and females

Question 7

autosome

Answer 7

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

Question 8

heterogametic sex

Answer 8

the sex (male or female) that produces two types of gametes with respect to sex chromosomes

Question 9

homogametic sex

Answer 9

the sex (male or female) that produces gametes that are all alike with regard to sex chromosomes

Question 10

pseudoautosomal region

Answer 10

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

Question 11

genic sex determination

Answer 11

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

Question 12

sequential hermaphroditism

Answer 12

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

Question 13

Turner syndrome

Answer 13

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

Question 14

Klinefelter syndrome

Answer 14

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

Question 15

triple-X syndrome

Answer 15

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

Question 16

sex-determining region (SRY) gene

Answer 16

gene on the Y chromosome that triggers male development

Question 17

sex-linked characteristic

Answer 17

characteristic determined by a gene or genes on sex chromosomes

Question 18

X-linked characteristic

Answer 18

characteristic determined by a gene or genes on the X chromosome

Question 19

Y-linked characteristic

Answer 19

characteristic determined by a gene or genes on the Y chromosome

Question 20

hemizygosity

Answer 20

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

Question 21

nondisjunction

Answer 21

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

Question 22

dosage compensation

Answer 22

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

Question 23

Barr body

Answer 23

inactivated X chromosome that appears as a condensed, darkly staining structure in most cells of female placental mammals

Question 24

Lyon hypothesis

Answer 24

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