Sex Determination and Sex Chromosomes

These flashcards cover key concepts related to sex determination and sex chromosomes, focusing on definitions, processes, and examples from various species.

Sex determination

The mechanism by which an individual develops into a female or male.

Sex chromosomes

Chromosomes that are different in males and females, such as X and Y.

X chromosome

One of the two sex chromosomes in humans; females have two Xs (XX).

Y chromosome

The sex chromosome that determines male characteristics in mammals; typically paired with an X (XY).

Heterogametic sex

The sex that produces two different types of gametes with respect to sex chromosomes (e.g., males with X and Y).

Homogametic sex

The sex that produces gametes with the same type of sex chromosome (e.g., females with XX).

SRY gene

A gene on the Y chromosome responsible for male development.

X-0 sex determination

A sex determination system where males have only one X chromosome (X0) and females have two Xs (XX).

Z-W sex determination

A system where males are homogametic (ZZ) and females are heterogametic (ZW), found in birds and some fish.

Haplodiploidy

A sex determination system based on the number of chromosome sets; males are haploid and females are diploid.

Temperature-dependent sex determination

A system where the sex of an organism is determined by the incubation temperature of the eggs, as seen in some reptiles.

Dioecious plants

Plants where individual organisms are either male or female.

Monoecious plants

Plants that have both male and female reproductive structures in the same individual.

Barr body

The inactivated X chromosome in female mammals, which appears condensed.

Dosage compensation

The mechanism that balances the expression of X chromosome genes between sexes.

Lyon Hypothesis

The theory that one X chromosome is randomly inactivated in female mammals during early development.

Calico cat

A female cat that has patches of different colors due to X-inactivation affecting coat color genes.

XXY individuals

Individuals with two X chromosomes and one Y chromosome who are phenotypically male.

XO individuals

Individuals with a single X chromosome who are typically female in the X-0 sex determination system.

Autosome

Any chromosome that is not a sex chromosome; humans have 22 pairs of autosomes.

Allosome

The sex chromosomes that determine sex; specifically, XX for female and XY for male.

Protandrous hermaphrodites

Organisms that can change sex from male to female, such as clownfish.

Species-specific mechanisms

Various mechanisms of dosage compensation vary among different animal species.

XY sex determination

Found in mammals where the presence of a Y chromosome determines maleness.

Behavioral interactions

Social cues that may influence the determination of sex in some species.

Chromosome sets

Refers to the number of homologous pairs of chromosomes present in an organism.

Environmental sex determination

Sex determination influenced by environmental factors, such as temperature or social interactions.

Fertilized eggs

Eggs that have been successfully combined with sperm to create a zygote.

Non-sex chromosomes

Chromosomes that do not determine sex and are part of the autosome sets.

Mitosis

The process by which a cell divides its nucleus and DNA to produce two identical daughter cells.

Meiosis

The process of cell division that produces gametes, reducing chromosome number by half.

XY ratio

In the X-0 system, the ratio of X chromosomes to autosomes determines sex.

XX ratio

In the X-0 system, having two X chromosomes with respect to autosomes typically results in a female.

Genetic traits

Characteristics influenced by specific genes located on chromosomes.

Chromosomal abnormalities

Variations in chromosome number or structure that can affect the development of the organism.

Sex-linked inheritance

The inheritance of genes that are located on sex chromosomes.