Sex Chromosomes: Dosage Compensation

These flashcards cover key concepts from Chapter 22 on sex chromosomes and dosage compensation.

Dosage Compensation

A biological mechanism that balances the gene dosage between sexes by managing the expression of sex-linked genes.

X-inactivation

The process by which one of the two X chromosomes in female mammals is randomly inactivated, resulting in dosage compensation.

Barr Body

The condensed, inactive X chromosome in female cells, which is typically not expressed.

XIST gene

A gene that plays a crucial role in X-inactivation by producing RNA that coats the inactive X chromosome.

Orange Gene (O)

An X-linked gene in cats that determines fur color, resulting in orange pigmentation if present in the active X chromosome.

F8 gene

An X-linked gene in humans responsible for producing Factor VIII, crucial for blood clotting.

Gene Dosage Problem

The issue resulting from unequal numbers of sex chromosomes in males and females, which may affect phenotype if gene dosage is not compensated.

Mosaicism

A condition in which an organism contains genetically different cells derived from the same zygote, often due to X-inactivation.

Chimera

An organism composed of genetically distinct cells derived from more than one zygote.

Gynandromorph

An organism that exhibits both male and female characteristics, often resulting from an early developmental error in sex chromosome segregation.

Hormonal Mechanism

A system of sex determination where hormones guide the development of sexual characteristics in an organism.

Cell-Autonomous Mechanism

A system of sex determination whereby individual cells independently determine their sex without hormonal influence.

Pseudoautosomal Regions

Regions on sex chromosomes that are not subject to X-inactivation and may express alleles from both X chromosomes.

Freemartin

A type of chimera found in female cattle, characterized by masculinized behavior and infertility due to sharing of tissues with a male twin.