Saved Which of the following statements about DNA replication is FALSE? 1) DNA synthesis on the lagging strand is discontinuous. 2) DNA replication can only proceed in the 3′ to 5′ direction. 3) DNA replication uses the rules of complementary base pairing to determine the sequence of the newly synthesized strand. 4) DNA replication is a process that occurs with high fidelity. 5) DNA replication is semi-conservative.
The Correct Answer and Explanation is:
The false statement is:
2) DNA replication can only proceed in the 3′ to 5′ direction.
Explanation:
DNA replication is a highly coordinated and regulated process that allows for the accurate duplication of the genome. Here’s a breakdown of each statement:
- DNA synthesis on the lagging strand is discontinuous:
This is TRUE. During DNA replication, the lagging strand is synthesized in short fragments known as Okazaki fragments. These fragments are later joined together by DNA ligase to form a continuous strand. This occurs because DNA polymerase can only add nucleotides in the 5′ to 3′ direction, and the lagging strand runs in the opposite direction (3′ to 5′), causing the need for discontinuous synthesis. - DNA replication can only proceed in the 3′ to 5′ direction:
This statement is FALSE. DNA replication actually proceeds in the 5′ to 3′ direction on both strands. DNA polymerase adds new nucleotides to the 3′ end of the growing strand, meaning that the direction of synthesis is 5′ to 3′. However, the template strand is read in the 3′ to 5′ direction to ensure the proper sequence of the new strand. - DNA replication uses the rules of complementary base pairing to determine the sequence of the newly synthesized strand:
This is TRUE. DNA replication follows the principle of complementary base pairing: adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C). The template strand dictates the sequence of the new strand based on these pairing rules. - DNA replication is a process that occurs with high fidelity:
This is TRUE. DNA replication is an extremely accurate process, with proofreading mechanisms to ensure the correct nucleotide is incorporated. DNA polymerase also has exonuclease activity to correct any errors made during replication. - DNA replication is semi-conservative:
This is TRUE. In semi-conservative replication, each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This was demonstrated by the famous Meselson-Stahl experiment.
Thus, statement 2 is the false one, as DNA polymerase adds nucleotides in the 5′ to 3′ direction, not the other way around.
