Transcription, RNA Processing and Control of Gene Expression Flashcards Preview

Biochem Final > Transcription, RNA Processing and Control of Gene Expression > Flashcards

Flashcards in Transcription, RNA Processing and Control of Gene Expression Deck (25)
1

What are three important differences between RNA and DNA?

1) RNA is single-stranded
2) RNA has uracil instead of thymine
3) RNA contains ribose instead of deoxyribose

2

What are the nucleotide donors for RNA?

ATP, GTP, UTP, CTP

3

Which polymerase is associated with rRNAs?

mainly Pol I, some Pol III

4

Which polymerase is associated with tRNAs?

Pol III

5

Which polymerase is associated with mRNAs?

Pol II

6

How does alpha-amanitin work?

Death cap mushroom
- potent inhibitor of Pol II, which blocks synthesis of mRNAs

7

Which type of RNA is the most abundant?

rRNA

8

How can rifampicin kill certain bacteria but have low toxicity against humans?

It is a potent inhibitor of RNA polymerase found in bacteria, therefore do not affect eukaryotic Pol II

9

What are the three modifications needed in order for mRNA to leave the nucleus?

In this specific order:
1) 5' methylguanosine cap
2) splicing, leaving only exons
3) poly-A tail
These processes mark the mRNA 'mature' and ready for transport out of the nucleus

10

Which disease is result of incorrect splicing, caused by a mutation in the gene that altered the nucleotide sequence at the first exon/intron boundary resulting in the destruction of the consensus sequence required for correct splicing?

Beta-thalassemia

11

Which disease is a result of a mutation that caused a single base change in the 5' splice donor site of one particular intron leading to defective splicing and production of a truncated protein that lacks one exon, which gets rapidly degraded?

Phyenylketouria (PKU)

12

Which type of histone modification acetylates lysine residues in histones and what does it result?

HATs (histone acetyltransferases)
- loosens up the DNA/histone modification
- facilitates transcription

13

Which type of histone modification deacetylates lysine residues in histones and what does it result?

HDACs (histone deacetyltransferases)
- tightens up DNA/histone modification
- inhibits transcription

14

In which base does DNA methylation occur?

cytosine

15

What are large protein complexes that use the energy from ATP hydrolysis to change nucleosome structure temporarily to pack DNA more tightly to the histone core or unpack so the DNA is more accessible?

chromatin remodeling complexes

16

Where do DNA-binding proteins bind to regulate transcription?

major groove

17

Example of a helix-turn-helix protein

homeobox proteins

18

What an example of zinc finger proteins?

glucocorticoid receptor

19

What's an example of leucine zipper proteins?

Fos and Jun

20

Where are cortisol receptors normally hang out at?

cytoplasm

21

The glucocorticoid receptor enters the nucleus as what structure once its's been activated by its ligand cortisol?

homodimer

22

Once the homodimer glucocorticoid receptor have formed, how does it regulate transcription once it enters the nucleus?

It is a zinc finger protein and binds to DNA at GRE (glucocorticoid responseive element) region and recruits HAT to facilitate transcription

23

Which cellular compartment are thyroid hormone receptors found?

nucleus

24

How does the thyroid hormone receptor act as a repressor?

- the receptor exist as a heterodimer (thyroid hormone receptor + retinoid X receptor)
- in the absence of thyroid hormone, the receptor recruits HDAC that represses transcription

25

How does PKA regulate transcription?

1) cytoplasm - cAMP levels rise due to glucagon signal. this activates PKA
2) activated PKA enters the nucleus and phosphorylates CREB
3) phosphorylated CREB binds to CRE (located in DNA)
4) the complex recruits CBP that also binds
5) CBP recruits EP300
6) the whole complex has the same function as HAT and regulates transciption