Question

Which one contains four pyrimidine bases?
A. GATCAATGC
B. GCUAGACAA
C. UAGCGGUAA
D. TGCCTAACG

Answer 1

Hint: Nucleotides are the building blocks of cell's DNA and RNA. Nucleic acids have five distinct nucleotide bases. There are three pyrimidines and two purines. Purine bases include adenine and guanine.

Complete Answer:
- Nucleic acids are polynucleotide chains where ribonucleotide and deoxyribonucleotide are monomeric units of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) respectively.
- Nucleotides consist of three components: the heterocyclic ring structure, the pentose sugar and the phosphate group. Because of their chemically simple nature, they are referred to as nitrogenous bases. These nitrogenous bases are responsible for the essential biological activities of nucleic acids.

- Nucleotide hydrolysis creates two forms of compounds derived from purine and pyrimidine heterocyclic rings known as purine and pyrimidine bases. Purines are obtained from pyrimidines by adding to the imidazole group.
- Purines and pyrimidines both have all their atoms in the same plane. Purines have a double ring while pyrimidines are a single ring structure. Purine has a ring of pyrimidine attached to the ring of imidazole.
- The pyrimidine only has a ring containing pyrimidine. Thus, purine has four nitrogen atoms, while pyrimidine has two.

The pyrimidine bases are thymine, cytosine, and uracil. In GATCAATGC, four pyrimidine bases are present, two thymines and two cytosines.

Thus, the correct answer is option A i.e., GATCAATGC.

Note: A purine is attached to pyrimidine by hydrogen bonds. Two hydrogen bonds attach Adenine to thymine while there are three hydrogen bonds between guanine and cytosine. In RNA, uracil replaces thymine.