Question

Assertion: Purine bases present in DNA are adenine and guanine.
Reason: The bases thymine is present in RNA while base uracil is present in DNA.
A. Both assertion and reason are correct and reason is the correct explanation for assertion
B. Both assertion and reason are correct but reason is not the correct explanation for assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

Answer 1

Hint: In order to answer this question, we must have the knowledge of the structures of DNA (deoxy ribonucleic acid) and RNA (ribonucleic acid). It is found that the nitrogenous bases that are purine and pyrimidine are present in nucleic acids.

Complete Solution :
- As we know that nitrogenous bases are of two types that are: purine and pyrimidine. Pyrimidine bases are the ring compounds that contain five membered nitrogens. Whereas, purine bases are six membered.
- Further purine bases are of two types adenine (A), guanine (G). Pyrimidine bases are of three types thymine (T), cytosine (C), uracil (U).
- It is found that in RNA, adenine (A), guanine (G), uracil (U), cytosine (C) are present.
- It is found that in DNA, adenine (A), guanine (G), thymine (T), cytosine (C) are present.
- Hence, we can conclude that the correct option is (C), that is Assertion is correct but Reason is incorrect.
So, the correct answer is “Option C”.

Note: - As we know that both RNA and DNA serve as the hereditary unit. We must remember that uracil is present in RNA, and RNA is a single stranded structure. Whereas, DNA is having a double helix structure.