02.15 - Eukaryotic Transcriptional Processing

Question 1

This refers to all the RNAs synthesised by a cell or organism.

Answer 1

Transcriptome

Question 2

It is the set of protein sequences that can be derived by translation of all protein-coding genes of a completely sequenced genome.

Answer 2

Proteome

Question 3

True or False: mRNA levels are not well-correlated with protein levels.

Answer 3

True

Question 4

True or False: Epigenetic changes involve changes in the underlying DNA sequence of the organism.

Answer 4

False

Question 5

Which chromatin structure is actively transcribed? Transcriptionally silenced?

Answer 5

Euchromatin, heterochromatin

Question 6

It refers to the number of copies of a certain gene present within an individual cell of an organism.

Answer 6

Gene dosage

Question 7

Which of the following is incorrect?

a. Genes for rRNA, which are expressed at high levels, must have multiple copies.
b. In human cells, 5 rDNA clusters are found in chromosomes 13, 14, 15, 21 and 22.
c. Gene amplification is always beneficial for an organism
d. Multiple drug resistance may be caused by amplification of genes that code for pumps.

Answer 7

c. Gene amplification is always beneficial for an organism

Question 8

It is the selective increase in number of a certain gene without affecting the quantity of the other genes.

Answer 8

Gene amplification

Question 9

What gene is amplified in breast cancer?

Answer 9

HER-2/neu or erbB-2

Question 10

What is the protein product of HER-2/neu?

Answer 10

Epidermal growth factor receptor-2

Question 11

Which of the following does not lead to breast cancer?

a. Increase in epidermal growth factor receptors in the cells
b. HER dimerization
c. Binding of herceptin to EGFR-2
d. Cross-phosphorylation of HER2-HER3 heterodimers

Answer 11

c. Binding of herceptin to EGFR-2

Question 12

In eukaryotes, in which part of the cell does transcription happens? Translation?

Answer 12

Nucleus, cytosol

Question 13

Enumerate the basic post-transcriptional modifications that are performed on the primary mRNA transcripts

Answer 13

5’ capping
3’ polyadenylation
Intron removal
Alternative splicing

Question 14

These are consensus sequences that serves as the binding site for RNA polymerase and general transcription factors.

Answer 14

Promoters

Question 15

These are transcription factor binding sites that are located anywhere in the gene and serves to increase promoter effectiveness and stimulate transcription.

Answer 15

Enhancers

Question 16

These are DNA sequences that binds with transcription regulation factors that prevents RNA polymerase from binding to the promoter.

Answer 16

Silencers

Question 17

Which of the following statements is incorrect?

a. Enhancer sequences can stimulate transcription at start sites thousands of bases away.
b. Chromosomal translocation of the proto-oncgene myc near the immunoglobulin enhancer may cause lymphoma or leukaemia.
c. Pax6 is a transcription factor that exhibits high specificity for a single enhancer sequence.
d. Promoters and enhancers are cis-acting elements, while RNA and proteins are trans-acting elements.

Answer 17

c. Pax6 is a transcription factor that exhibits high specificity for a single enhancer sequence.

Question 18

True or False: Trans-acting factors control gene expression by binding to cis-acting factors.

Answer 18

True

Question 19

Which of the following is incorrect?

a. 5’ cap enhances translation of mRNAs by eukaryotic translation machinery.
b. The 5’ cap is characterised by a unique 5’-5’ triphosphate linkage.
c. The stop codon serves as a signal for polyadenylation.
d. The spliceosome is composed of snRNA and proteins.

Answer 19

c. The stop codon serves as a signal for polyadenylation. (The polyadenylation signal sequence is AAUAAA.)

Question 20

What are the three general mechanisms for localisation of mRNAs?

Answer 20

Directed transport via cytoskeleton
Random diffusion and trapping
Generalized degradation + local protection

Question 21

Which of the following statements is incorrect?

a. mRNA translation should be silenced as it travels from the nucleus to the cytoplasm.
b. Oocytes store some mRNAs in inactivated form, which are only activated after fertilisation.
c. The poly A tail are the target binding sites of miRNAs.
d. Translation of cytoskeleton-attached bicoid mRNA leads to bicoid protein gradient in the fertilised egg of Drosophila.

Answer 21

c. The poly A tail are the target binding sites of miRNAs. (The 3’ UTR is the target binding site of miRNAs.)

Question 22

Arrange the steps of RNA interference in order:

I - Formation of siRNA-RISC complex
II - Cleavage of dsRNA into siRNA
III - Formation of single stranded RNA (ssRNA) + RISC complex
IV - Complementary binding of ssRNA-RISC to mRNA
V - Cleavage of target mRNA

a. II-III-I-IV-V
b. II-I-III-IV-V
c. II-III-I-V-IV
d. I-II-III-V-IV

Answer 22

b. II-I-III-IV-V