Question

Okazaki fragments during DNA replication

• A. Polymerise in 3' $\to$ 5' direction and form replication fork
• B. Prove semiconservative DNA replication
• C. Short, newly synthesized DNA fragments that are formed on the lagging template strand
• D. Cause transcription process

Answer 1

The correct option is C Short, newly synthesized DNA fragments that are formed on the lagging template strand

DNA synthesis always occurs in the 5'-->3' direction because chain growth results from the formation of a phosphodiester bond between the 3' oxygen of a growing strand and $\alpha$ phosphate of a dNTP; option A is incorrect.

To facilitate the growth of the lagging strand in the 5'-->3' direction, copying of its template strand must somehow occur in the opposite direction from the movement of the replication fork, i.e., in 3’ to 5’ direction; option C is correct. This is done by synthesizing a new primer every few hundred bases on the second parental strand. Each of these primers is elongated in the 5'-->3' direction and form discontinuous segments called Okazaki fragments which are later joined together by DNA ligase.

The semiconservative mechanism of DNA replication in which a DNA strand serves as a template for the synthesis of a new strand and produces two new DNA molecules, each with one new strand and one parental strand, is followed by both DNA strands. Option B is incorrect. Transcription is the process of RNA synthesis using DNA template strand which is carried out by RNA polymerase; any of two DNA strands can serve as the template, option D is incorrect. The correct answer is C.