Sex Determination and Sex Chromosomes

Vocabulary flashcards covering key concepts from Chapter 7 of Concepts of Genetics related to sex determination and chromosomes.

Primary sexual differentiation

Involves only the gonads where gametes are produced.

Secondary sexual differentiation

Involves the overall appearance of the organism.

Unisexual (dioecious)

Individuals that contain only male or female reproductive organs.

Bisexual (monoecious)

Individuals that contain both male and female reproductive organs.

Asexual reproduction in Chlamydomonas

Involves organisms spending most of their life cycle in the haploid phase, producing daughter cells by mitotic division.

Isogametes

Gametes that are not usually morphologically distinguishable and can fuse together during mating.

Mating types of Chlamydomonas

Two haploid gametes, mt- and mt+, which can only mate with each other.

Sporophyte stage in maize (Zea mays)

Diploid stage where both male and female structures are present.

C. elegans

A nematode worm with two sexual phenotypes: males (only testes) and hermaphrodites (both testes and ovaries).

Self-fertilization in hermaphrodites

Occurs in C. elegans, producing primarily hermaphrodite offspring.

Protenor mode of sex determination

Depends on random distribution of X chromosomes into male gametes, leading to male or female offspring.

Lygaeus mode of sex determination

Involves male gametes having either an X or a Y chromosome, resulting in male or female offspring.

Heterogametic sex

The sex that produces two different types of gametes with respect to sex chromosomes.

Homogametic sex

The sex that produces gametes that are all the same with respect to sex chromosomes.

Klinefelter Syndrome

A condition in males characterized by the presence of extra X chromosomes, such as XXY.

Turner syndrome

A condition in females characterized by the absence of one X chromosome; typically 45,XO karyotype.

47,XXX syndrome

A condition where females have an extra X chromosome; can lead to underdeveloped sexual characteristics or may be asymptomatic.

47,XYY condition

A condition where males have an extra Y chromosome; related to tall height and potential subnormal intelligence.

Male Specific Region of Y (MSY)

Non-recombining region of the Y chromosome critical for male development.

SRY gene

Sex-determining region of the Y chromosome that triggers testes formation.

Dosage compensation

Mechanism that balances the expression of X-linked genes between males and females.

Barr bodies

Inactivated X chromosomes that are highly condensed, observed in female cells.

Lyon hypothesis

Posits that X-inactivation is random in somatic cells during embryonic development.

X-inactivation center (Xic)

Region on the X chromosome that initiates X inactivation.

The ratio of X chromosomes to autosomes in Drosophila

Determines sex; does not involve Y chromosome.

Temperature-dependent sex determination (TSD)

System in some reptiles where the incubation temperature of eggs determines sex.

Critical period of embryonic development

Time during which temperature affects the sex determination of reptile embryos.

Male gametes in sex determination

Produces equal numbers of X- and Y-bearing sperm with equal viability.

Secondary sex ratio

Reflects the proportion of each sex that is born.

X-linked genes

Genes located on the X chromosome that can affect sex-related traits.

Diploid zygote

Result of the fusion of two haploid gametes, containing two sets of chromosomes.

X chromosome dosage compensation

Prevention of excessive expression of X-linked genes in females through X chromosome inactivation.