Review for Lecture 16 and 17
Regulation of Gene Expression/Viruses
To Know:
Define “gene expression”.
The steps at which gene expression can be regulated:
Step 1 – Chromatin structure – acetylation and methylation of histones
Step 2 – Transcription – sequence-specific (or cell-specific) transcription factors
Step 3 – Post-transcriptional Regulation – splicing
Step 4 and 5 – mRNA stability and Translation – microRNAs
Step 6 – Protein Stability – ubiquitination and degradation through the
Proteasome
Define oncogene and proto-oncogene.
As you may have noticed I may favor Step 2 and Step 4 and 5……
Describe how the trp operon is regulated – what happens in the absence of tryptophan
and in the presence of tryptophan? Do the same for the lac operon - what happens in the
absence of lactose and in the presence of lactose?
Questions.
1. Condensed chromatin inhibits:
A. tRNA
B. RNA polymerase
C. translation
D. assembly of transcription factors
2. When tryptophan is present in the medium for bacteria, the tryptophan binds
to
A. trp operon
B. trp promoter
C. trp operator
D. trp repressor
E. trp polymerase
3. The assembly of general transcription factors on a promoter begins
approximately 25 nucleotides upstream of the coding sequence, where TBP
binds to the sequence:
A. ATAT
B. AATT
C. TTAA
D. TAAT
E. TATA
4. In order for a gene to be transcribed, RNA polymerase must have access to the
DNA and be able to bind to the
A. activator
B. regulator
C. promoter
D. operator
E. repressor
5. The association of chromatin with DNA is weakened by
A. acetylation
B. ubiquitination
C. pH
D. DNA sequence
E. Deacetylation
6. Name the two types of transcription factors that bind to a promoter.
7. What is lost from the pre-mRNA during splicing – introns or exons?
8. A gene has the following structure:
A
B
C
TATA
box
coding sequence
If a liver cell contains transcription factors that bind to site A and C in the
promoter, but kidney cells do not, then in which cells do you expect this
gene to be expressed? Why? What is the purpose of the transcription
factors that bind to site A and C? What binds to the TATA box? What
enzyme is responsible for RNA synthesis?
9. If the gene described in number 8 is transcribed in skin cells, but no protein can
be detected, what are two possible reasons for the lack of protein.
10. The signal transduction protein ras can exist as a proto-oncogene and an
oncogene. What is the difference between a proto-oncogene and an oncogene?
What is the effect of oncogenic ras?
11. What specific enzyme is able to synthesize DNA using RNA as a template?