This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Gene Expression Control – Transcriptional-level Control”.
1. Which technology can be used to monitor thousands of genes in a single experiment?
b) Polymerase chain reaction
c) DNA microarrays
d) RNA microarrays
Explanation: DNA microarrays (or “DNA chips”) is the technology that can be used to monitor the expression of thousands of genes expressed in a cell population, in a single experiment.
2. How many types of transcription factors assist in transcription-level control?
Explanation: There are 2 types of Transcription factors: Basal level and Regulatory. They bind with RNA polymerase and regulate its binding therefore controlling the rate of gene expression.
3. Sequence-specific transcription factors can act as transcriptional activators or repressors.
Explanation: Sequence-specific transcription factors can act as transcriptional activators by stimulation the expression of adjacent gene or as transcriptional repressors by inhibiting its transcription.
4. What percent of genes encode transcription factors?
Explanation: Approximately 5 to 10 percent of the genome encodes for transcription factors. One transcription factor interacts with more than one DNA sequence.
5. Which cells are pluripotent?
b) embryonic stem cells
Explanation: Embryonic stem cells appear very early in the development of a mammalian embryo and possess two very unique properties, indefinite self-renewal and capability of differentiating into different cell types.
6. Importance of transcription factors in embryonic stem cells was demonstrated in ______________
Explanation: Stem cells from chicken and murine embryos were extensively studied by Shinya Yamanaka and Kazutoshi Takahashi and in 2006 they published a paper regarding the role of transcription factors in stem cells.
7. In cellular reprogramming, which of the following is removed during chromatin reorganization?
a) epigenetic marks
Explanation: During cellular reprogramming, the epigenetic marks that include histone modifications and DNA methylation patterns of differentiated cells are replaced with that of pluripotent cells.
8. How many domains are present in a transcription factor?
Explanation: The transcription factors usually contain two domains, activation domain that interacts with other DNA-binding proteins thereby regulating transcription, and DNA-binding domain that binds to the DNA sequence.
9. Motifs are related structures present on the transcription factors constituting the _________________ domain.
c) RNA-binding domain
d) Nucleic acid-binding
Explanation: The DNA-binding domains of various transcription factors contain related structures (believed to be conserved through evolutionary period) called motifs. The most common motifs in eukaryotes include zinc finger, the helix–loop–helix, and the leucine zipper.
10. In the leucine-zipper motif, leucine occurs after every ____ amino acids.
Explanation: In the leucine-zipper motif, the leucines occur every seventh amino acid along the length of alpha-helix. The alpha-helix is the part of the DNA-binding domain that fits into the major groove of DNA.
11. One of the key-enzymes involved in gluconeogenesis is ______________
a) phosphoenolpyruvate carboxykinase
b) phosphoenolpyruvate carboxylase
c) phosphoenolpyruvate ethanol
d) phosphoenolpyruvate esterase
Explanation: One of the key enzymes involved in the metabolic pathway that converts pyruvate to glucose (gluconeogenesis) is phosphoenolpyruvate carboxykinase, synthesized in the liver when glucose levels are low.
12. Core promoter is the site that stretches between _______________
a) TATA box and start site
b) TATA box and stop site
c) TATA box and operator
d) TATA box and the promoter
Explanation: Core promoter is the region upstream of a gene that stretches between the TATA box and the transcription start site. It is the site of assembly for pre-initiation complex consisting of RNA polymerase II and general transcription factors that are required for eukaryotic gene transcription.
13. CAAT and GC box are ________________
a) stop codons
b) promoter sequences
c) inhibitor sequences
d) operator sequences
Explanation: Like TATA box, CAAT and GC box are short promoter sequences that are located farther upstream of the gene. These sequences are often required by the polymerase to initiate transcription of the gene.
14. Which of the following is a transcription factor widely employed in eukaryotic gene expression?
Explanation: NF1 is a transcription factor that binds to CAAT and GC boxes, found in many tissues and widely employed in eukaryotic gene expression.
15. TATA box regulates the frequency with which the gene is transcribed.
Explanation: TATA box determines the site of the ignition of transcription whereas the frequency with which RNA polymerase transcribes a gene is determined by the CAAT and GC boxes.
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