Question

Mode of DNA replication in Escherichia coli is

• A. Conservative and unidirectional
• B. Semi-Conservative and unidirectional
• C. Conservative and bidirectional
• D. Semi-conservative and bidirectional

Answer 1

The correct option is D

Semi-conservative and bidirectional

The correct option is option D.

Explanation of the correct option:

1. In Escherichia coli DNA replication is semi-conservative and bidirectional.
2. In 1958, Matthew meselson and Stahl experimented on Escherichia coli.
3. This experiment proved that in newly synthesized DNA one strand is parental and one is the new one.
4. The double-stranded DNA becomes uncoiled at the time of replication and both strands are separated.
5. Both strands act as a template and complementary DNA strands are synthesized.
6. DNA replication is bidirectional. DNA replication starts at a point and DNA replicates in two directions.

Explanation of the incorrect options:

Option A:

1. Conservative replication means both strands are newly synthesized and parental DNA is not separated.
2. Unidirectional replication means DNA replicates only in one direction. This is not found in E.coli.

Option B: DNA replication in E.coli is semi-conservative but not unidirectional.

Option C: DNA replication in E.coli is bidirectional but not conservative.

Final answer: Mode of DNA replication in Escherichia coli is semi-conservative and bidirectional.