Explanation: Heterogeneous nuclear RNA (hnRNA) is the precursor to mRNA in eukaryotes. It contains both introns and exons and undergoes processing (splicing, capping, and polyadenylation) to form mature mRNA, which is then translated into protein.
- During protein synthesis, what is the function of the ribosome?
a) It transcribes mRNA from DNA
b) It links amino acids together to form a polypeptide chain
c) It transports amino acids to the growing polypeptide chain
d) It synthesizes tRNA molecules
Answer: b) It links amino acids together to form a polypeptide chain
Explanation: The ribosome is the cellular machinery responsible for translating mRNA into a protein. It facilitates the formation of peptide bonds between amino acids, creating a polypeptide chain.
- Which of the following types of RNA carries the genetic code from the nucleus to the ribosome for protein synthesis?
a) tRNA
b) mRNA
c) rRNA
d) siRNA
Answer: b) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic information transcribed from DNA in the nucleus to the ribosome, where it is translated into a protein.
- In the lac operon, when lactose is present:
a) The repressor protein binds to the operator
b) The repressor protein is inactivated by lactose
c) RNA polymerase is blocked from transcribing the genes
d) Glucose inhibits the operon
Answer: b) The repressor protein is inactivated by lactose
Explanation: When lactose is present, it binds to the repressor protein, causing a conformational change that inactivates the repressor. This allows RNA polymerase to bind to the promoter and transcribe the genes needed to metabolize lactose.
- In DNA, the pyrimidine bases are:
a) Adenine and guanine
b) Cytosine and thymine
c) Adenine and thymine
d) Cytosine and guanine
Answer: b) Cytosine and thymine
Explanation: Pyrimidine bases in DNA are cytosine and thymine. Adenine and guanine are purine bases. Pyrimidines have a single-ring structure, while purines have a double-ring structure.
- Which of the following RNA molecules is part of the spliceosome complex?
a) mRNA
b) tRNA
c) rRNA
d) snRNA
Answer: d) snRNA
Explanation: Small nuclear RNA (snRNA) is a component of the spliceosome, the complex responsible for splicing introns from pre-mRNA in eukaryotic cells.
- Which of the following processes is responsible for increasing the variability in eukaryotic gene expression by producing different proteins from the same gene?
a) Transcription
b) Translation
c) Alternative splicing
d) RNA editing
Answer: c) Alternative splicing
Explanation: Alternative splicing is a process by which different combinations of exons are joined together to produce multiple proteins from the same pre-mRNA, thus increasing the diversity of proteins a single gene can encode.
- Which of the following sequences can be recognized as the start codon in both prokaryotes and eukaryotes?
a) UAG
b) AUG
c) UGA
d) UAA
Answer: b) AUG
Explanation: AUG is the start codon in both prokaryotes and eukaryotes, coding for the amino acid methionine, which initiates protein synthesis.
- Which type of mutation is caused by the insertion or deletion of nucleotides that is not in multiples of three?
a) Missense mutation
b) Nonsense mutation
c) Silent mutation
d) Frameshift mutation
Answer: d) Frameshift mutation
Explanation: Frameshift mutations occur when nucleotides are inserted or deleted in numbers that are not multiples of three, shifting the reading frame of the codons and potentially altering every downstream amino acid.
- Which of the following enzymes is responsible for transcribing tRNA?
a) RNA polymerase I
b) RNA polymerase II
c) RNA polymerase III
d) DNA polymerase
Answer: c) RNA polymerase III
Explanation: RNA polymerase III transcribes transfer RNA (tRNA) and other small RNAs like 5S rRNA. RNA polymerase II transcribes mRNA, and RNA polymerase I transcribes rRNA.
- Which of the following genetic elements is NOT involved in regulating gene expression in the lac operon?
a) Operator
b) Promoter
c) Repressor
d) Enhancer
Answer: d) Enhancer
Explanation: Enhancers are distant regulatory sequences that increase the transcription of eukaryotic genes. In the lac operon, gene expression is regulated by the promoter, operator, and repressor, but enhancers are not involved.
Leave a comment