DNA duplication occurs at which of the following stages?
A) Meiosis II
B) Mitotic interphase
C) Mitosis only
D) Both meiosis and mitosis

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Hint: The process by which the double stranded DNA is copied to produce two identical copies of DNA is known as DNA replication.

Complete Answer:
Before finding the right option, let us first understand what meiosis and mitosis is. So, meiosis is the process by which a single cell undergoes division twice in order to give rise to four daughter cells which contain half the genetic information. Meiosis occurs in sex cells- eggs in females and sperms in males.
Whereas, mitosis is the process by which a single cell undergoes a single division and produces only two daughter cells which have the same amount of genetic information as the parent.

Option a: Meiosis II is similar to that of mitosis with only exception that it does not have ‘S’ phase. In meiosis II, the sister chromatids present in the two daughter cells separate and form four gametes. These gametes have only half the genetic information of the parent, i.e. they are haploid. No DNA replication takes place here. Therefore, this is the incorrect option.

Option b: It is during mitosis, i.e interphase takes place between one mitotic phase and the next mitotic phase. Hence this option is not suitable.

Option c: In mitosis, the DNA replicates during the interphase.

Option d: In meiosis, the genetic material, i.e. the DNA undergoes replication in the S or the Synthesis phase of meiosis. Whereas in case of mitosis, DNA replication happens during the interphase. Therefore, this is the correct option.

Thus, the correct option is d) Both meiosis and mitosis.

Note: When you look at the question you may feel that all options except option a is correct. But one thing to be noted is that, option d is more suited as it has both meiosis and mitosis.