Free Ribonucleic Acid (RNA) MCQs with Answers

1. Which statement about RNA is correct?

• A. It contains thymine in place of uracil
• B. It contains ribose and is usually single stranded
• C. It is always double stranded like DNA
• D. It contains deoxyribose and uracil

Explanation: RNA carries ribose, which has a hydroxyl group at carbon 2, and it is normally a single strand that can fold back on itself, as tRNA does into its clover leaf shape. Uracil replaces thymine in RNA, not the other way round, and deoxyribose belongs to DNA. The extra hydroxyl is also why RNA is chemically less stable than DNA.

2. The function of transfer RNA during protein synthesis is to

• A. carry the genetic message out of the nucleus
• B. form the structural core of the ribosome
• C. unwind the DNA double helix
• D. bring the correct amino acid to the ribosome according to the codon being read

Explanation: Each tRNA carries an anticodon at one end and its matching amino acid at the other, so it acts as the adaptor that translates the language of bases into the language of amino acids. Messenger RNA is the molecule that carries the message from the nucleus, and ribosomal RNA forms the structure of the ribosome, so all three types work together. Unwinding DNA is the job of helicase.

3. Messenger RNA differs from transfer RNA in that mRNA

• A. carries a copy of the base sequence of a gene from the nucleus to the ribosome
• B. is folded into a clover leaf shape
• C. carries an anticodon at one end
• D. is the most abundant type of RNA in the cell

Explanation: Messenger RNA is transcribed from one strand of a gene and is read in triplets by the ribosome, so its length varies with the gene it copies and it is usually short lived. The clover leaf shape and the anticodon belong to transfer RNA, and ribosomal RNA is the most abundant type by mass. Because mRNA is a working copy, the original DNA is never exposed to the risks of the cytoplasm.

4. Transcription produces

• A. A DNA copy of DNA
• B. An RNA copy of DNA
• C. A protein from DNA
• D. A DNA copy of RNA

Explanation: Transcription is the synthesis of RNA using DNA as a template, catalyzed by RNA polymerase.

5. The start codon is

• A. UAA
• B. AUG
• C. UAG
• D. UGA

Explanation: AUG codes for methionine and serves as the start codon, initiating protein synthesis.

6. Introns are

• A. Coding sequences
• B. Non-coding sequences removed during splicing
• C. Found only in prokaryotes
• D. Essential for translation

Explanation: Introns are non-coding intervening sequences removed during RNA splicing; exons are joined together.

7. Which is a stop codon?

• A. AUG
• B. UAA
• C. UUU
• D. GGC

Explanation: UAA, UAG, and UGA are stop codons (nonsense codons) that terminate translation.

8. Which of the following is the correct higher (left) to lower (right) sequence of molecules with respect to their amount in the cell?

• A. DNA to rRNA to tRNA to mRNA
• B. rRNA to tRNA to mRNA to DNA
• C. mRNA to tRNA to rRNA to DNA
• D. DNA to mRNA to tRNA to rRNA

Explanation: This is the order given in the official UHS answer key. Among the three RNAs the ranking is not disputed: ribosomal RNA is by far the most abundant at roughly 80 per cent of cellular RNA, transfer RNA follows, and messenger RNA is the smallest fraction because it is made as needed and degraded quickly. Placing DNA at the head reflects the paper's intent that the genome is the largest single nucleic acid component.

9. Which of the following is a key feature of RNA?

• A. Deoxyribose and thymine
• B. Double stranded and thymine
• C. Ribose and uracil
• D. Ribose and thymine

Explanation: RNA carries ribose, which has a hydroxyl group at carbon 2, and uses uracil in place of thymine, and it is normally single stranded. Deoxyribose and thymine are the DNA features, so options mixing one sugar with the wrong base can be eliminated at once. The extra hydroxyl is also why RNA is chemically less stable than DNA.

10. Which of the following types of RNA makeup the largest proportion of total cellular RNA?

• A. Messenger RNA
• B. Ribosomal RNA
• C. Transfer RNA
• D. Catalytic RNA (ribozyme)

Explanation: Ribosomal RNA accounts for roughly 80 per cent of the RNA in a cell, because every ribosome is built largely from it and a busy cell contains millions of ribosomes. Transfer RNA comes next at around 15 per cent, and messenger RNA is a small and rapidly turning over fraction. Ribozymes are rarer still.