17 past paper MCQs on Ribonucleic Acid (RNA), from the Biological Molecules unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.Which of the following is the correct higher (left) to lower (right) sequence of molecules with respect to the amount in the cell? (UHS MDCAT 2025)
Correct answer: (b) rRNA → tRNA → mRNA → DNA
About four fifths of the RNA of a cell is ribosomal, then transfer, then messenger, and DNA is a different molecule altogether.
2.Which of the following is a key feature of RNA? (UHS MDCAT 2025)
Correct answer: (c) Ribose and uracil
RNA carries ribose in place of deoxyribose and uracil in place of thymine.
3.Which of the following types of RNA makeup the largest proportion of total cellular RNA? (UHS MDCAT 2025)
Correct answer: (b) Ribosomal RNA
Ribosomal RNA is the bulk of the cell’s RNA because ribosomes are so numerous.
4.The main role of mRNA during protein synthesis is to: (UHS MDCAT 2025)
Correct answer: (a) Carry genetic information for protein synthesis
Messenger RNA carries the base sequence of a gene from the nucleus to the ribosome.
5.The structure of RNA consists of: (KMU MDCAT 2025)
Correct answer: (d) Base pairing instead of thymine
RNA is a single strand carrying ribose, and uracil takes the place of thymine.
6.Which process uses mRNA to make protein at ribosomes? (SIBA MDCAT 2025)
Correct answer: (c) Translation
Translation is the reading of messenger RNA into a chain of amino acids at the ribosome.
7.Which of the following is the best alternative term for ATP? (PMC MDCAT 2022)
Correct answer: (c) Nucleoside triphosphate
ATP is adenosine, a nucleoside, carrying three phosphate groups.
8.If an mRNA consists of 150 nucleotides, how many amino acids would be present in the polypeptide which is encoded by this mRNA? (PMC MDCAT 2022)
Correct answer: (a) 50
Three bases code for one amino acid, so $150/3$ is fifty.
9.Transcription is the process in which an RNA copy of the DNA sequence and coding the gene is produced with the help of an enzyme called: (PMC MDCAT 2020)
Correct answer: (b) RNA polymerase
RNA polymerase reads the template strand and builds the RNA copy.
10.Which statement correctly describes the transcription of DNA? (PMC MDCAT 2020)
Correct answer: (b) It produces messenger RNA
Transcription copies a gene into messenger RNA.
11.NAD is an example of: (PMC MDCAT 2020)
Correct answer: (b) Dinucleotide
NAD is two nucleotides joined through their phosphates.
12.Sequence of amino acids, in a polypeptide chain of protein molecule, corresponds to the sequence of nucleotides on mRNA for that protein. If the reading frame of mRNA for a human protein is 993 nucleotides, including a stop codon at the end, how many amino acids would be incorporated in the polypeptide chain? (UHS MDCAT 2019)
Correct answer: (b) 330
$993/3$ is $331$ codons, of which the last is a stop, so $330$ amino acids.
13.The process in which a complementary copy of the code from a gene is produced by RNA Polymerase in the nucleus: (UHS MDCAT 2019)
Correct answer: (a) Transcription
Copying a gene into RNA is transcription.
14.Which one is an example of a Nucleotide? (UHS MDCAT 2019)
Correct answer: (c) ATP
A nucleotide is a base, a sugar and a phosphate; ATP is adenosine with three phosphates.
15.If sequence in DNA is CCCTAGAG, then what would be the sequence in messenger RNA after transcription ? (UHS MDCAT 2019)
Correct answer: (a) GGGAUCUC
RNA pairs G with C and A with U, so CCCTAGAG is transcribed as GGGAUCUC.
16.The process in which an RNA copy of the DNA sequence encoding the gene is produced (UHS MDCAT 2017)
Correct answer: (b) Transcription
Copying a gene into RNA is transcription.
17.In translation, the termination codon is: (UHS MDCAT 2017)
Correct answer: (a) UAA
UAA, UAG and UGA are the stop codons.