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Biochemistry > 4. RNA Structure and Synthesis > Flashcards

4. RNA Structure and Synthesis Flashcards

0
Q

Is RNA single stranded or double stranded

A

Single

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1
Q

Is this topic more important than DNA

A

Yes

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2
Q

Why is RNA liable to NaOH

A

because of the presence of a OH group at position 2

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3
Q

classes of RNA

A 
rRNA, mRNA, tRNA 
small nuclear RNAs 
small nuclear ribonucleoproteins - snRNPs 
microRNAs - miRNAs 
small interfering RNAs
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4
Q

composition of prokaryotic RNAs

A

50s + 30s =70s

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5
Q

composition of eukaryotic RNAs

A

60s + 40s = 80s

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6
Q

shape of tRNA

A

clover leaf shape

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7
Q

what RNA carries genetic information from nuclear DNA to the cytosol

A

mRNA

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8
Q

what constitutes RNA polymerase

A

sigma factor, 2 alphas, one beta and one beta prime

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9
Q

function of the sigma factor

A

enables RNA polymerase to recognize and bind more tightly to promoter regions on the DNA

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10
Q

characteristics of RNA polymerase (prokaryotic)

A

syntehesizes RNA in the 5’-3’ direction
Does not require a primer
has no exonuclease or endonuclease activity
no ability to repair mistakes

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11
Q

3 parts of transcription

A

Initialtion, elongation. termination

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12
Q

promoter regions

A

sequences in DNA that determine the start point and the frequency of transcription (located short distance upstream from where transcription starts

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13
Q

consensus sequences

A

when the codon is not 100% like the pribnow

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14
Q

pribnow

A

TATAAT

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15
Q

what step of transcription does rifampicin act?

A

Initiation

16
Q

what occurs that causes the enzyme to enter elongation mode

A

release of sigma factor

17
Q

what enzyme is used in elongation

A

ribonucleotide triphosphates

18
Q

2 modes of termination

A

rho dependent and rho independent

19
Q

features of rho dependent

A

regularly spaced C residues that rho factor binds to

It is a hexameric protein

20
Q

features of rho independent termination

A

involves a consensus sequence (inverted repeats) followed by poly U
RNA polymerase pauses after it synthesizes that RNA

21
Q

how does Actinomycin D act

A

interfere with the movement of RNA polymerase along the DNA

22
Q

what does acetylation of histones do

A

leads to activation of gene expression

23
Q

what is the most significant effect of histone modification?

A

ability to attract specific proteins to a stretch of chromatin.

24
Q

Are histone modifications reversible?

A

Yes

25
Q

how are acetyl groups added to lysines

A

histone acetyl transferases

26
Q

how are acetyl groups removed from lysines

A

histone deacetylase complexes

27
Q

where does methylation of DNA occur

A

CG sequence

28
Q

what does methylation of eukaryotic DNA do

A

decreases transcriptional activity - by preventing the binding of transcription factors

29
Q

what is the function of chromatin remodeling

A

provides rapid access to many specific DNA sequences

30
Q

RNA polymerase

A

used in transcription of tRNA genes, must be initiated by general transcription factors TFIIIC and TFIIIB

31
Q

what facilitates the binding of RNA polymerase

A

transcription factors that bind to the TATA box

32
Q

What are enhancers?

A

regulatory cis-acting DNA sequences

33
Q

silencers

A

reduce the level of gene expression

34
Q

4 thngs that must be added to prokaryotes in post translational modification

A

5’ capping
RNA Splicing
3’ poly adenylation
RNA cap

35
Q

what is 5’ capping

A

addition of 7 guanosine to 5’ terminal end

36
Q

what enzyme catalyses methylation of guanine in cytosol

A

guanine-7-methyltransferease

37
Q

what are the splicing donors

A

GU at the 5’

an adenosine at the branch point

38
Q

what is the splice acceptor

A

AG at the 3’

Biochemistry (7 decks)

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