The Ras Protein Is a GTPase That Functions in Many

question 29

Multiple Choice

The Ras protein is a GTPase that functions in many growth factor-signaling pathways.In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bound, the signal is not transmitted.Mutations in the gene for Ras are found in many cancers.Of the choices below, which alteration of Ras activity is most likely to contribute to the uncontrolled growth of cancer cells?

• A)a change that prevents Ras from being made
• B)a change that increases the affinity of Ras for GDP
• C)a change that decreases the affinity of Ras for GTP
• D)a change that decreases the rate of hydrolysis of GTP by Ras

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Definitions:

Colostrum

The first form of milk produced by the mammary glands of mammals immediately following delivery of the newborn, rich in antibodies.

Antibodies

Proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses.

Lactose

A disaccharide sugar derived from galactose and glucose that is found in milk, used by the body as a source of energy.

Somatic Cells

Any cell of the body that makes up the tissues, organs, and parts of the body, excluding the reproductive cells.