- Which of the following is true about introns and exons?
a) Introns are coding regions and exons are non-coding regions
b) Exons are coding regions and introns are non-coding regions
c) Both introns and exons are non-coding regions
d) Introns and exons are not found in eukaryotic DNA
Answer: b) Exons are coding regions and introns are non-coding regions
Explanation: In eukaryotic genes, exons are coding regions that are spliced together to form mature mRNA, while introns are non-coding regions that are removed during RNA processing.
- What role does RNA polymerase play in transcription?
a) It unwinds the DNA double helix
b) It adds amino acids to the growing protein chain
c) It synthesizes RNA from a DNA template
d) It connects Okazaki fragments
Answer: c) It synthesizes RNA from a DNA template
Explanation: RNA polymerase synthesizes RNA by using one strand of DNA as a template during transcription.
- Which of the following is a feature of the genetic code?
a) It is ambiguous
b) It is overlapping
c) It is universal
d) It is not degenerate
Answer: c) It is universal
Explanation: The genetic code is almost universal, meaning the same codon codes for the same amino acid in nearly all organisms, from bacteria to humans. It is also degenerate (multiple codons code for the same amino acid) and non-overlapping.
- In a DNA molecule, if the sequence of one strand is 5’-ATTGCA-3’, what is the complementary sequence of the other strand?
a) 5’-TAACGT-3’
b) 3’-TAACGT-5’
c) 5’-UAACGU-3’
d) 3’-AUUGCA-5’
Answer: b) 3’-TAACGT-5’
Explanation: DNA strands are complementary and antiparallel. Adenine pairs with thymine, and guanine pairs with cytosine. The complementary sequence to 5’-ATTGCA-3’ is 3’-TAACGT-5’.
- Which of the following enzymes seals the gaps between Okazaki fragments during DNA replication?
a) DNA polymerase
b) DNA ligase
c) Primase
d) Helicase
Answer: b) DNA ligase
Explanation: DNA ligase joins the Okazaki fragments on the lagging strand during DNA replication by forming phosphodiester bonds between adjacent nucleotides.
- The process by which RNA is synthesized from a DNA template is called:
a) Translation
b) Replication
c) Transcription
d) Splicing
Answer: c) Transcription
Explanation: Transcription is the process where a single strand of DNA serves as a template for the synthesis of RNA, mediated by RNA polymerase.
- What is the role of a promoter in transcription?
a) It terminates transcription
b) It synthesizes RNA
c) It initiates transcription by binding RNA polymerase
d) It acts as a primer
Answer: c) It initiates transcription by binding RNA polymerase
Explanation: The promoter is a specific sequence of DNA that signals RNA polymerase to bind and begin transcription of the gene.
- Which of the following nitrogenous bases is unique to RNA?
a) Thymine
b) Adenine
c) Guanine
d) Uracil
Answer: d) Uracil
Explanation: In RNA, uracil replaces thymine and pairs with adenine. RNA contains the bases adenine, guanine, cytosine, and uracil.
- Which of the following is NOT a function of ribosomal RNA (rRNA)?
a) It provides the structural framework for ribosomes
b) It catalyzes the formation of peptide bonds
c) It carries amino acids to the ribosome
d) It helps position the mRNA for translation
Answer: c) It carries amino acids to the ribosome
Explanation: Transfer RNA (tRNA), not rRNA, is responsible for carrying amino acids to the ribosome during translation. rRNA plays a role in the structure of the ribosome and catalyzing peptide bond formation.
- The process by which mRNA is converted into a sequence of amino acids is called:
a) Replication
b) Translation
c) Transcription
d) Splicing
Answer: b) Translation
Explanation: Translation is the process by which the sequence of codons in mRNA is read by the ribosome to assemble amino acids into a polypeptide chain (protein).
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