DNA replication is studied in a newly discovered bacterium. It takes 30 min for the bacterium to complete a round of replication at 37oC. A Meselson-Stahl-type experiment was performed. The bacteria were grown for several generations in 14N-medium and then switched to 15N-medium. The DNA molecules were then analyzed.

If the mechanism of DNA replication in this bacterium were semi-conservative, what results would be found when the double-stranded DNA was analyzed in a CsCl density gradient after three generations in 15N-medium?

#Question id: 1158

#Unit 4. Cell Communication and Cell Signaling

Muscarinic acetylcholine receptors are GPCRs that slow the rate of heart muscle contraction upon ligand binding/activation. Activation of this receptor leads to opening of potassium channels triggered by decreases in cAMP levels. The muscarinic acetylcholine receptor likely couples to:

#Question id: 1159

#Unit 4. Cell Communication and Cell Signaling

Cholera toxin can make you sick through overactivation of a Gs pathway even if your body stops making the ligand associated with activation of the pathway. Knowing this, which of the following CANNOT be true about cholera toxin?

#Question id: 1160

#Unit 4. Cell Communication and Cell Signaling

Signal amplification is an important part of GPCR-mediated signaling. Which of the following steps do NOT directly amplify the signal?

#Question id: 1161

#Unit 4. Cell Communication and Cell Signaling

A mutation renders a Gαq subunit constitutively active (also known as dominant active). Which of the following effects might you observe in a cell with this mutation?

#Question id: 1162

#Unit 4. Cell Communication and Cell Signaling

Diacylglycerol (DAG) formation aids in cell signaling by:

#Question id: 1163

#Unit 4. Cell Communication and Cell Signaling

β-blockers inhibit an adrenergic receptor found on many cell types in the body, including heart cells. Patients who have arrhythmias (irregular heartbeats) most likely benefit from what downstream action of these drugs?