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In Meselson and Stahl's experiment, equa...

In Meselson and Stahl's experiment, equal amount of light DNA and heavy DNA was observed in E.coli culture after
I. Two generation
II. 40 minutes
III. 80 minutes
IV. Three generation
Choose the correct option for given statement of question.

A

I and II

B

II and III

C

III and IV

D

I and IV

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question regarding Meselson and Stahl's experiment and the observation of equal amounts of light DNA and heavy DNA in E. coli culture, we can break down the solution into clear steps: ### Step-by-Step Solution: 1. **Understanding the Experiment**: Meselson and Stahl conducted an experiment to demonstrate the semi-conservative replication of DNA. They used two isotopes of nitrogen: N15 (heavy) and N14 (light) to label the DNA. 2. **Initial Setup**: In the beginning, E. coli was grown in a medium containing N15, which incorporated into the DNA, making it heavy. After several generations, the DNA was solely heavy. 3. **First Generation**: When the E. coli was transferred to a medium containing N14, the DNA replication process began. In the first generation after the switch, each DNA molecule consisted of one heavy strand (from N15) and one light strand (from N14), resulting in hybrid DNA. 4. **Second Generation**: After one more generation (40 minutes later), the hybrid DNA from the first generation replicated. This time, half of the DNA molecules were hybrids (one heavy and one light), and the other half were completely light (N14). At this point, there were equal amounts of light and hybrid DNA. 5. **Conclusion**: Therefore, equal amounts of light DNA (N14) and hybrid DNA (N15/N14) were observed after two generations (which corresponds to 40 minutes after the switch to N14 medium). ### Answer: The correct options for the statement are: - I. Two generations - II. 40 minutes ### Final Answer: The correct option is: **I and II**. ---
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