Question

In their experiment to prove DNA replication is semi-conservative, Meselson and Stahl used 6M \(\text{CsCl}\) because the density gradient value of 6M \(\text{CsCl}\) is ________ the density gradient value of \({}^{15}\text{N}\) DNA.

• A. almost equal to
• B. double
• C. half
• D. one fourth to

Hint:

In density gradient centrifugation, DNA settles where the CsCl density equals the DNA density.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
In density gradient centrifugation, DNA settles at the position in the tube where the CsCl solution has the same density as the DNA.

Step 2: Choice of CsCl
The density of 6 M CsCl is close to the density of DNA, including the heavy \({}^{15}\text{N}\) DNA, so both heavy and light DNA form separate bands within the gradient.

Step 3: Conclusion
So the density gradient value of 6M CsCl is almost equal to that of \({}^{15}\text{N}\) DNA.

Final Answer:
The density of 6M CsCl is almost equal to that of \({}^{15}\text{N}\) DNA. \[ \boxed{\text{(A) }\text{almost equal to}} \]