Question

The correct statement with regard to the secondary structure of DNA/RNA is:

• A. DNA possesses a single strand helix structure and contains uracil as one of the four bases.
• B. DNA possesses a double strand helix structure and contains thymine as one of the four bases.
• C. RNA possesses a double strand helix structure and contains uracil as one of the four bases.
• D. RNA possesses a single strand helix structure and contains thymine as one of the four bases.

Hint:

DNA is double stranded and contains thymine, whereas RNA is usually single stranded and contains uracil.

Answer 1

The Correct Option is B

Step 1: Understanding the Topic:
This question deals with "Biomolecules," particularly the structural features of nucleic acids: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid). Nucleic acids are the information-carrying molecules of the cell. Their secondary structure describes the spatial arrangement of the nucleotide strands and the specific hydrogen-bonding patterns between nitrogenous bases. Differentiating between DNA and RNA structural characteristics is a fundamental concept in molecular biology and biochemistry.
Step 2: Key Formulas and Approach:
The approach involves identifying the specific differences between DNA and RNA in terms of:
The number of strands in the helix.
The specific nitrogenous bases present (specifically the difference between Thymine and Uracil).

Step 3: Detailed Explanation:

DNA Characteristics: DNA is composed of two polynucleotide chains that wrap around each other to form a double-strand helix. The four nitrogenous bases in DNA are Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). The two strands are held together by complementary base pairing (A with T, G with C).
RNA Characteristics: RNA is generally a single-strand molecule. While it can fold back on itself to form complex 3D shapes, its standard secondary structure is a single polynucleotide chain. The nitrogenous bases in RNA are Adenine (A), Guanine (G), Cytosine (C), and Uracil (U). Note that Uracil replaces Thymine in RNA.
Evaluating Statements:
(A) Incorrect because RNA contains Uracil, not Thymine.
(B) Correct because DNA is double-stranded and uses Thymine.
(C) Incorrect because RNA is usually single-stranded.
(D) Incorrect because DNA is double-stranded and uses Thymine.

Step 4: Final Answer:
The correct description is provided in option (B).