Evolutionary Tracing Has Identified Clusters of the Most Invariant Amino

question 38

Multiple Choice

Evolutionary tracing has identified clusters of the most invariant amino acids in the SH2 domain family. Which of the following is true regarding these sites?

• A) Mutation in these sites generally keeps the protein functional.
• B) The invariant amino acids generally have negatively charged side chains.
• C) These sites correspond to the binding site for peptides containing phosphorylated tyrosine.
• D) The amino acids at these sites are generally hydrophobic.
• E) These sites have evolved fast because they have critical functions.

---

Definitions:

Homeostasis

The self-regulating process by which biological systems maintain stability while adjusting to conditions that are optimal for survival.

Blood-Brain Barrier

The blood-brain barrier is a selective semipermeable border that prevents most substances in the blood from entering the brain, thus protecting it from pathogens and toxins while allowing essential nutrients to pass through.

Cortisol

A steroid hormone in the body, often released in response to stress and used as a marker for stress levels.

Corticotropin-Releasing Hormone

A hormone involved in the stress response, stimulating the pituitary gland to release adrenocorticotropic hormone, which then promotes the production of cortisol by the adrenal glands.