Which of the following statements about DNA replication is false?
DNA is synthesized in the 5′ ?to 3′ ?direction.
The lagging strand grows overall at its 5′ ?end.
DNA synthesis is a conservative process.
The two replication forks at a replication origin move in opposite directions.
The Correct Answer and Explanation is :
Correct Answer:
“DNA synthesis is a conservative process.”
Explanation:
DNA replication is semiconservative, not conservative. This means that when DNA replicates, each of the two new DNA molecules consists of one original (parental) strand and one newly synthesized strand. This was demonstrated by the famous Meselson-Stahl experiment, which disproved the conservative model.
Here’s an explanation of why the other statements are true:
- DNA is synthesized in the 5′ to 3′ direction.
DNA polymerase adds nucleotides to the 3′ hydroxyl (-OH) end of the growing strand. This means that new DNA strands always elongate in the 5′ to 3′ direction. This is a fundamental property of DNA replication. - The lagging strand grows overall at its 5′ end.
Because DNA polymerase can only synthesize DNA in the 5′ to 3′ direction, the lagging strand is synthesized in short fragments called Okazaki fragments, which are later joined by DNA ligase. These fragments are synthesized in the 5′ to 3′ direction, but overall, the lagging strand grows toward its 5′ end. - The two replication forks at a replication origin move in opposite directions.
DNA replication is bidirectional, meaning that two replication forks are formed at the origin of replication, moving away from each other in opposite directions.
Thus, the incorrect statement is the one that suggests DNA replication is a conservative process, which is false. Instead, semiconservative replication ensures genetic continuity from one generation to the next.
Now, I’ll generate an image illustrating DNA replication, showing the leading and lagging strands, replication fork, and direction of synthesis.
Here is an illustration of DNA replication, depicting the replication fork, leading and lagging strands, Okazaki fragments, and the direction of synthesis. Let me know if you need any modifications or further explanations!
