Read the passage given below and answer the following question.
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids found in living systems. DNA acts as the genetic material in most of the organisms. RNA though it also acts as a genetic material in some viruses, mostly functions as a messenger. RNA has additional roles as well. It functions as adapter, structural, and in some cases as a catalytic molecule. The chemical structure of a polynucleotide chain (DNA or RNA). A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. There are two types of nitrogenous bases – Purines and Pyrimidines.
Which of the following is not a component of a nucleotide?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Histone
The passage states that “A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group.”
A nucleotide is the unit from which DNA and RNA are built. A base joined to the sugar forms a nucleoside, and adding a phosphate group makes a nucleotide. Histones are not part of it. They are positively charged basic proteins, rich in lysine and arginine. In eukaryotes, the negatively charged DNA wraps around a core of eight histone molecules (the histone octamer) to form a nucleosome.
Option (1) Pentose sugar — A component of a nucleotide. It is ribose in RNA and deoxyribose in DNA.
Option (2) Histone — Not a component of a nucleotide. It is a protein that packages DNA.
Option (3) Nitrogenous base — A component of a nucleotide. It is a purine or a pyrimidine.
Option (4) Phosphate group — A component of a nucleotide. It links one nucleotide to the next in the chain.