A nucleic acid was analyzed and found to contain 32% adenine, 18% guanine, 17% cytosine and 33% thymine. The nucleic acid must be –
**Question:** A nucleic acid was analyzed and found to contain 32% adenine, 18% guanine, 17% cytosine, and 33% thymine. The nucleic acid must be -
A. Deoxyribonucleic Acid (DNA)
B. Ribonucleic Acid (RNA)
C. DNA with some inverted base pairs
D. RNA with some inverted base pairs
**Correct Answer:** D. Ribonucleic Acid (RNA) with some inverted base pairs
**Core Concept:**
Nucleic acids are essential biological molecules that play a crucial role in the storage and transmission of genetic information in living organisms. They consist of nucleotides, which are composed of a sugar molecule (deoxyribose or ribose), a phosphate group, and a nitrogenous base. There are two main types of nucleic acids: Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA). DNA contains adenine (A), thymine (T), guanine (G), and cytosine (C), with a specific ratio: A:T ~ 1:1 and G:C ~ 1:1. In contrast, RNA has a different base composition: adenine (A), guanine (G), cytosine (C), and uracil (U), with a different ratio: A:U ~ 1:1 and G:C ~ 1:1.5.
**Why the Correct Answer is Right:**
The nucleic acid in question contains adenine (A) at a percentage of 32%, guanine (G) at a percentage of 18%, cytosine (C) at a percentage of 17%, and thymine (T) at a percentage of 33%. Comparing these percentages to the standard nucleotides in DNA and RNA, we can deduce that the nucleic acid is RNA.
In DNA, the base ratio is A:T ~ 1:1, while in RNA, the base ratio is A:U ~ 1:1. The ratio of G:C in DNA is 1:1, whereas in RNA, it is 1:1.5. The presence of uracil (U) in RNA explains the higher G:C ratio in RNA (1:1.5).
**Why Each Wrong Option is Incorrect:**
A. DNA: In DNA, A:T ratio is 1:1, which is not the case here (32% A, 18% G, 17% C, and 33% T).
B. RNA: The presence of thymine (T) in the nucleic acid is correct, but the overall base composition does not match RNA (32% A, 18% G, 17% C, and 33% T).
C. DNA with inverted base pairs: DNA has a fixed base ratio (A:T ~ 1:1, G:C ~ 1:1). The nucleic acid described has an inverted base ratio (32% A, 18% G, 17% C, and