Select The Most Correct Statement Regarding Nucleic Acids:
A. DNA And RNA Both Contain The Sugar Deoxyribose.
B. DNA Is A Long, Double-Stranded Molecule Made Up Of A, U, G, And C Bases.
C. RNA Is A Long, Single-Stranded Molecule Made Up Of The Bases A, U, G, And C Bases.
D. RRNA Is A Molecular Molecule That Is A Copy Of DNA
The Correct Answer and Explanation is:
Correct Answer: C. RNA Is A Long, Single-Stranded Molecule Made Up Of The Bases A, U, G, And C Bases.
Explanation:
Nucleic acids are large biomolecules essential for the storage and expression of genetic information. There are two major types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Each plays a critical role in the central dogma of molecular biology — DNA makes RNA, and RNA makes proteins.
Option A is incorrect because DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. The presence or absence of one oxygen atom on the sugar distinguishes the two: ribose has a hydroxyl group (-OH) on the 2’ carbon, while deoxyribose lacks this group (hence “deoxy”).
Option B is incorrect because DNA does not contain uracil (U). The four nitrogenous bases in DNA are adenine (A), thymine (T), guanine (G), and cytosine (C). DNA is typically double-stranded and has a helical structure known as the double helix.
Option C is correct. RNA is usually single-stranded and consists of the nitrogenous bases adenine (A), uracil (U), guanine (G), and cytosine (C). In RNA, uracil replaces thymine and pairs with adenine during transcription. RNA molecules can vary in length and function but are generally single-stranded, unlike the double-helix of DNA.
Option D is misleading. While rRNA (ribosomal RNA) is a type of RNA transcribed from DNA, describing it as “a copy of DNA” is oversimplified. rRNA is specifically synthesized from DNA genes coding for ribosomal RNA but undergoes processing and does not serve the same informational role as mRNA. Therefore, it is not accurate to say rRNA is a copy of DNA.
In summary, option C is the most accurate statement, reflecting both the structure (single-stranded) and the composition (A, U, G, and C) of RNA.