Chromosomes, meiosis, & X-inactivation

What are autosomes?

Chromosomes other than the sex chromosomes.

What separates during meiosis I?

Homologous chromosomes.

What separates during meiosis II?

Sister chromatids.

When does crossing over occur?

Prophase I of meiosis.

What is nondisjunction?

Failure of chromosomes or chromatids to separate properly.

What is trisomy?

Three copies of a particular chromosome.

What is monosomy?

One copy of a particular chromosome instead of two.

What is a Barr body?

A condensed, largely inactivated X chromosome.

What is dosage compensation?

Balancing X-linked gene expression between individuals with different numbers of X chromosomes.

Is every gene on an inactive X completely silent?

No. Some genes escape X-inactivation.

Why can calico cats have patches of different colors?

Different cell groups inactivate different X chromosomes.