Question

Which of the following is not a component of DNA?

• A. Thiamine
• B. Adenine
• C. Guanine
• D. Cytosine

Answer 1

The Correct Option is A

To determine which of the options is not a component of DNA, we need to review the basic components of DNA. DNA is composed of nucleotides, which are the building blocks. Each nucleotide consists of three components:

• A phosphate group
• A sugar molecule (deoxyribose)
• A nitrogenous base

There are four types of nitrogenous bases found in DNA:

• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Thymine (T)

In the given options:

• Adenine
• Guanine
• Cytosine
• Thiamine

Three of these are nitrogenous bases in DNA, but "Thiamine" is not one of them. Thiamine is a vitamin (also known as Vitamin B1) and not related to DNA structure.

Components	Type
Adenine	Nitrogenous base in DNA
Guanine	Nitrogenous base in DNA
Cytosine	Nitrogenous base in DNA
Thiamine	Vitamin (not part of DNA)

Therefore, the option which is not a component of DNA is: Thiamine.

Answer 2

The components of DNA include four nitrogenous bases:

• Adenine (A)
• Thymine (T)
• Guanine (G)
• Cytosine (C)

These bases pair as follows:

• Adenine pairs with Thymine (A-T)
• Guanine pairs with Cytosine (G-C)

Thiamine is not a component of DNA. It is a vitamin (specifically, vitamin B1) and does not appear in the structure of DNA. The correct component related to Thiamine is Thymine (which pairs with Adenine in DNA).

Thus, the correct answer is (1) Thiamine.