Unit 3: Cytogenetics Lecture #2 X Chromosome and X-Chromosome Inactivation

These flashcards cover key terms and concepts related to the X chromosome and its inactivation process as discussed in the cytogenetics lecture.

X Chromosome

The sex chromosome that spans about 155 million DNA base pairs and represents approximately 5% of the total DNA in cells.

Barr Body

A densely packaged, inactive X chromosome found in female mammalian cells.

Xist

X-Inactive Specific Transcript, a long non-coding RNA that plays a crucial role in the X chromosome inactivation process.

Dosage Compensation

The mechanism ensuring that cells of females and males have the same effective dose of X-linked genes despite females having two X chromosomes.

Epigenetic Marks

Chemical modifications on DNA and histones that regulate gene expression and are involved in the process of X-inactivation.

X Inactivation Center (XIC)

A DNA coding area essential for X chromosome inactivation, located on each X chromosome.

Skewed X Inactivation

A phenomenon where one X chromosome is preferentially inactivated over the other, leading to unequal expression of X-linked genes.

Random X Inactivation

The process by which either the maternal or paternal X chromosome is randomly chosen to be inactivated in female cells.

Rnf12

A gene that acts as a molecular sensor for multiple X chromosomes and regulates the expression of Xist.

Epigenetic Reprogramming

The process that occurs in primordial germ cells where previous X inactivation is cleared to ensure both X chromosomes are active prior to meiosis.