The four nucleotides are adenine (A), cytosine (C), guanine (G) and thymine (T).
(a) True
(b) False
The Correct Answer and Explanation is :
Answer: (a) True
The statement that the four nucleotides are adenine (A), cytosine (C), guanine (G), and thymine (T) is correct.
Nucleotides are the building blocks of nucleic acids such as DNA and RNA. Each nucleotide consists of three components: a phosphate group, a sugar molecule (either deoxyribose in DNA or ribose in RNA), and a nitrogenous base. The four nitrogenous bases that make up DNA are adenine, cytosine, guanine, and thymine. These bases are classified into two groups:
- Purines: These are adenine (A) and guanine (G), which have a two-ring structure.
- Pyrimidines: These are cytosine (C) and thymine (T), which have a single-ring structure.
In the structure of DNA, adenine always pairs with thymine (A-T), and cytosine always pairs with guanine (C-G). These base pairs are held together by hydrogen bonds and form the double helix structure that characterizes DNA.
In RNA, the nucleotide thymine (T) is replaced by uracil (U), so the four bases in RNA are adenine, cytosine, guanine, and uracil (A, C, G, U). In RNA, adenine pairs with uracil instead of thymine.
The sequence of these nucleotides along a DNA or RNA strand encodes genetic information. The specific order of nucleotides determines the instructions for building proteins, which are essential for the structure, function, and regulation of cells in living organisms.
Thus, the four nucleotides mentioned—adenine, cytosine, guanine, and thymine—are indeed the correct nitrogenous bases in DNA.