Chapter 5: Sex Determination

This set of flashcards contains key vocabulary terms and definitions related to sex determination from the lecture notes, designed to aid in review and understanding of the subject.

Sex determination

The mechanism by which an individual develops into an egg-producer (female) or a sperm-producer (male).

Autosomal chromosomes

Chromosomes that are not involved in sex determination.

Sex chromosomes

Chromosomes involved in sex determination, specifically X and Y chromosomes in humans.

Homogametic sex

In humans, females are the homogametic sex (XX), meaning they have two of the same sex chromosomes.

Heterogametic sex

In humans, males are the heterogametic sex (XY), meaning they have two different sex chromosomes.

SRY gene

A gene found on the Y chromosome that is responsible for male development.

Difference in sex development (DSD)

A condition where individuals have variations in sex development that do not fit typical definitions of male or female.

Hemizygous

The condition of having only one allele for a gene in an individual, as seen in XY males for X-linked genes.

Barr body

An inactivated X chromosome found in female cells, which is dense chromatin and explains dosage compensation.

Lyon hypothesis

The hypothesis proposed by Mary Lyon that one of the two X chromosomes in a female mammal is randomly inactivated.

Dosage compensation

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

X-inactivation center (Xic)

A region of the X chromosome that contains the Xist gene, responsible for X chromosome inactivation.

X-linked recessive

An inheritance pattern where the trait is rare in females, may skip generations, but commonly affects males.

X-linked dominant

An inheritance pattern where the trait is usually present in every generation, affecting males and their daughters.

Pseudoautosomal regions (PARs)

Regions on the Y chromosome that share homology with regions on the X chromosome and synapse with it during meiosis.

Calico cat

A cat with a coat featuring orange and black patches, illustrating the Lyon hypothesis on X-linked traits.

Mosaic

An organism with two or more genetically different cell lines, as seen in females with multiple X chromosomes.

Meiosis

The process of cell division that reduces the chromosome number by half, leading to the formation of gametes.

Xist gene

A gene expressed on the inactivated X chromosome involved in the process of X-inactivation.

Drosophila melanogaster

A species (fruit fly) used in genetic studies that demonstrates different mechanisms of dosage compensation.

Caenorhabditis elegans

A species (roundworm) where XX individuals are hermaphrodites and demonstrate unique gene expression patterns.

X-linked gene

A gene located on the X chromosome, which exhibits different inheritance patterns than autosomal genes.