Question

You learn that a Mars lander has retrieved a bacterial sample from the polar ice caps. You obtain a sample of these bacteria and perform the same kind of experiment that Meselson and Stahl did to determine how the Mars bacteria replicate their DNA. Based on the following equilibrium density gradient centrifugation results, what type of replication (conservative, semiconservative or Dispersive) would you propose for these new bacteria?

Answer 1

Answer:

a. conservative replication

b. semi conservative replication

c. dispersive replication

d. discontinuous replication

e. continuous replication

The CORRECT ANSWER IS C.

c. dispersive replication

Explanation:

The attached image shows a single band that becomes lighter (in volume) and increase in darker intensity (in times of color) is revealed with consecutive replications. The major pattern that would produce these outcome is dispersive replication.

Conservative replication do reveal two bands (a 14N for the wholly latest molecule, and a 15N for the totally antiquated molecule) after the initial replication. Therefore, this wholly wrong.

Semi-conservative replication reveal an individual band of transitional weight after the initial  replication, followed by two bands following the second replication (one of transitional weight, and the other at the 14N position). These two bands is observed in each following replication, with the transitional weight becoming lighter in color as the 14N band is seen to appear darker in color.

The real pattern gives an individual band that pinpoints to all molecules in an individual replicative cycle possessing the same constituents.

Dispersive replication, has its molecules to be a blend of old (15N) and new (14N) strands. Each replication raises the ratio of new to old strands as it explains the reason an individual band is shown raised (lighter in weight) with every replication.