This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Gene Expression – Messenger RNA”.
1. When were the first structures of ribosomal subunits made by scientists?
Explanation: The first structures of ribosomal subunits were made in the year 2000 by scientists Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath, which is available in the Protein Data Bank.
2. The “S” in the 80S ribosomes stands for _______________
a) Svedberg’s units
b) Sedimentation coefficient
Explanation: “S” stands for Svedbergs, a measure of how fast the molecule moves in a centrifuge. The rate of sedimentation is related to the shape and size of the molecule.
3. Which of the following are precursors for mRNAs?
Explanation: Heterogeneous nuclear RNAs (hnRNA) are large molecular weight RNA molecules, present exclusively in the nucleus. They are precursors to the cytoplasmic mRNAs.
4. Which of the following has the smallest half life?
Explanation: Heterogeneous nuclear RNA (hnRNA) has the smallest half, it is processed into mRNAs shortly after or even during synthesis.
5. All mRNA precursors are synthesized by ___________________
a) RNA polymerase I
b) RNA polymerase II
c) RNA polymerase III
d) RNA polymerase IV
Explanation: All eukaryotic mRNA precursors are synthesized by RNA polymerase II, it is conserved from yeast to mammals.
6. Which of the following gene encodes for the white of a chicken egg?
Explanation: The gene that codes for the white of a chicken is ovalbumin. The promoter of this gene is located between 24 and 32 bases upstream in the region called TATA box.
7. TFIID is a ______________
a) protein complex
b) transcription factor
Explanation: Transcription factor for polymerase II, fraction D (TFIID) is a protein complex whose subunit is TATA-binding protein (TBP). Its function is to initiate accurate transcription of the mRNA.
8. Which enzyme unwinds the DNA?
Explanation: The enzymes that unwind the DNA are known as DNA helicases. Unwinding of DNA enables the access of polymerase.
9. More than one RNA polymerase can attach to the promoter site.
Explanation: For as long as a transcription factor for polymerase II, fraction D (TFIID), remains bound to the promoter additional RNA polymerase molecules are able to attach.
10. The RNA polymerase engaged in transcription is ________________
Explanation: The RNA polymerase engaged in transcription is heavily phosphorylated while the same enzyme assembled into the pre-initiation complex (PIC) is not phosphorylated.
11. Messenger RNAs are found in the ________________
Explanation: Messenger RNAs (mRNAs) are present in the cytoplasm and are attached to ribosomes where they are translated.
12. Eukaryotic mRNAs have special modifications, not present in prokaryotic mRNAs.
Explanation: Eukaryotic mRNAs have special modifications on 5’ and 3’ termini, which are not present in prokaryotic mRNAs or on rRNAs or tRNAs. These include poly(A) tail on 3’ end and methylated guanosine cap on 5’ end.
13. Genes with intervening (non-coding) sequences are called ___________________
c) split genes
d) jumping genes
Explanation: The genes with intervening, non-coding regions are called spit-genes. The coding part is called exon and non-coding part is called intron.
14. Which technique was used to find the relationship between 15S and 10S globin RNAs?
a) S-loop formation
b) R-loop formation
c) Pulsed-field gel electrophoresis
d) Polymerase chain reaction
Explanation: The technique known as R-loop formation was employed by Shirley Tilghman, Philip Leder, and their co-workers at the National Institutes of Health for discerning the relationship between 15S and 10S globin RNAs.
15. Which of the following prevents the digestion of mRNA by exonucleases?
a) methyl-guanosine cap
b) methylene blue
c) poly(A) tail
d) bromophenol blue
Explanation: The methylguanosine cap at the 5’ end of the mRNA prevents its digestion by the exonucleases and also plays an important role in the initiation of translation.
Sanfoundry Global Education & Learning Series – Cell Biology.
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