Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOL 361 EXAM 2 > Diverse Functions of RNAs > Flashcards

Diverse Functions of RNAs Flashcards

1
Q

all RNA’s are generated through transcription and are a ‘copy’ of a DNA portion, what are the 3 major differences between DNA and RNA?

A
  1. use ribose instead of deoxyribose
  2. uses uracil instead of thymine
  3. RNAs are single stranded
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the two types of RNA associated with DNA modifications and chromatin remodeling?

A
  1. siRNAs
  2. long non-coding RNAs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the two types of RNA associated with RNA processing?

A
  1. snRNAs (small nuclear RNA)
  2. snoRNAs (small nucleolar RNAs)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what RNA type is associated with protein coding?

A

mRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what type of RNA is associated with mRNA turnover?

A

siRNAs (small interfering RNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what type of RNA is associated with translation regualtion?

A

miRNAs (microRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what type of RNA is associated with ribosome structure in translation?

A

rRNAs (ribosomal RNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what type of RNA is associated with translation protein synthesis?

A

tRNAs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the two major control types that regulate protein production?

A
  1. transcriptional control
  2. post-transcriptional contorl
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the two major transcriptional controls?

A
  1. chromatin structure
  2. initiation of transcription (RNA polymerase, general transcription factors, and specific transcriptional regulators)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the 3 post transcriptional control mechanisms in protein production?

A
  1. splicing efficiency
  2. mRNA stability
  3. translational control (initiation of translation, translation efficiency)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the three steps in mRNA processing?

A
  1. 5’ capping (addition of methylguanosine)
  2. splicing
  3. 3’ polyadenylation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what enzymes are involved in 5’ capping during mRNA processing?

A
  1. phosphatase (removed 5’-P)
  2. guanyl transferase (adds G in 5’-5’ orientation)
  3. methyltransferase (adds methyl-group to base)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how does mRNA processing occur?

A

RNA Pol. II contains a long tail with tandem repeats with Ser at 2 and 5 position. The 5 position is phosphorylated during transcription initiation allowing the capping proteins to bind to Pol. The proteins then ‘jump’ to the 5’ end of the mRNA as it emerges from RNA Pol. coupling transcription with mRNA processing. The same principle is used for splicing and 3’-modification.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the two major steps to mRNA splicing?

A
  1. adenine base (near 3’ end of intron) attacks the 5’-end of the intron cutting it which covalently binds the 5’-base of teh intron forming a lariat
  2. the released 3’-OH of the exon reacts w the 3’ end of the intron. this cuts the last base of the intron and releases the intron as a lariate. following this the exon joins with the released 5’-phosphate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the two sequences of mRNA that be conserved for splicing to occur?

A
  1. intron/exon boundaries
  2. branch point
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

in mRNA splicing, splicing is facilitated by a large complex, what is it called?

A

a spliceosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how many snRNP are present in a spliceosome?

A

5 snRNP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

for each snRNP in a spliceosome, how many proteins are there?

A

7 proteins with 1 snRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

snRNAs are the core of the spliceosome and fold into a complex 3D-structure, what does it bind to form the snrNP?

A

it binds Sm protein ring to form snRNP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

in mRNA splicing what does U1 snRNP bind?

A

U1 snRNP base pairs to 5’-end of the intron to be spliced out

22
Q

in mRNA splicing there is a 5’-splic rearrangement where U1 is exchanged for U4/6 snRNP. why does this occur?

A

is a check and re-check strategy to ensure that the appropriate splice site is being targeted

23
Q

in mRNA splicing there is a branch point site rearrangement: BBB-> U2- snRNP. what does this achieve?

A

U2 snRNA pairs with branch-point, excluding and exposing the adenine that will form the lariat. this acts as another double check in the splicing process.

24
Q

what happens in mRNA splicing after both the 5’ splice rearrangement and the branch point site rearrangement have occurred?

A

U6 and U2 snRNA can pair with each other. this brings branch point A to exposed 5’ end of the intron allowing A to attach the 5’-G of intron and cause cleavage at the 5’ end of the intron.

25
Q

in mRNA splicing what is the rxn catalyzed by?

A

the reaction is catalyzed by the RNA, not a protein in the snRNP complex

26
Q

after mRNA splicing has been done, exon joining must happen. how does this occur?

A

U5 snRNA pairs with the 3’-end of the first exon keeping it in place. then U5 snRNA also pairs with the 5’-end of the second exon bringing it close to the 3’ end of the first exon then catalyzing the joining of the two exons.

27
Q

what occurs after mRNA splicing is finished?

A

polyadenylation of the mRNA tail

28
Q

in the polyadenylation process of the mRNA tail relatively few based are conserved. what is the conserved sequence recognized by initiation factors?

A

AAUAAA

29
Q

following the detection of the AAUAAA signal, where is the mRNA cleaved?

A

after CA 10-30 nt downstream.

30
Q

what two things are unique about polyA-polymerase?

A
  1. template independent
  2. adds ~ 200 A’s
31
Q

after the polyA tail is created by polyA-polymerase, what happens?

A

polyA tail is coated by polyA binding proteins that stabilize it

32
Q

mRNA’s have a short half-life (~30min), how does decay start?

A

decay starts gradually with poly A-shortening catalyzed by a specific exonuclease (deadenylase) essentially acting as a ‘count down timer’

33
Q

poly A-shortening competes with translation initiation, why is this?

A

because exonuclease binds to the cap the same way that translation initiation factors do so efficiently translate proteins have longer half lives

34
Q

what are the two degradation pathways of mRNA?

A
  1. de-capping, followed by 5’-3’ degradation
  2. continued 3’-5’ degradation
35
Q

the speed of the steps in the two mRNA degradation pathways are determined by what?

A

speed of each step is determined by actual mRNA sequence especially if the 3’-UTR contain specific protein binding domains thereby decreasing or increasing the rate of degradation

36
Q

mRNA decay can also be initiated by cleavage being catalyzed by sequence specific RNA endonuclease. what can regulate this?

A

by RNA binding proteins

37
Q

what is an example of when RNa binding proteins regulate mRNA decay due to cleavage?

A

cytosolic aconitase binds a specific RNA sequence located in the 5’-UTR and blocks the endonuclease site causing translation

38
Q

what is the main thing that cytosolic aconitase does?

A

it blocks the endonuclease site of the mRNA that translates transferrin receptors. this allows translation unless iron is present in the system which when bound to cytosolic aconitase RNa binding capacity is reduced and endonuclease can cleave the mRNA and degrade it

39
Q

what two things does cytosolic aconitase cause?

A
  1. it represses translation of ferritin unless bound by iron
  2. it stabilizes mRNa so transferrin receptors are transcribed. if bound by iron the mRNA degrades due to endonucleases
40
Q

translation is realized in ribosomes, what are the two sub-units called and what do they do?

A
  1. small subunit 40S: tRNa orientation
  2. large subunit 60S: catalysis of peptide bond formation in growing protein chain guided by tRNA/mRNa base pairing
41
Q

what makes up a ribonucleoprotein complex?

A

many proteins plus rRNAs

42
Q

about how much of the total RNA in a cell is made up by rRNAs?

A

~80% of the total RNA in a cell

43
Q

what are the three major differences between rRNA and mRNA?

A

1) rRNAs are transcribed as a single unit (except 5S rRNA)
2) They are not processed like mRNAs (no cap, no poly A tail)
3) Bases in precursor rRNA become modified either undergoing isomerization of U into pseudo-U or 2-methylation of ribose on the backbone.

44
Q

rRNA modifications are site specific, what are the modifications guided by?

A

they are guided by base-pairing with snoRNAs

45
Q

Approximately how many snoRNAs are there and what do they do?

A

~150 specific small nucleolar RNAs. snoRNAs assemble / guide proteins performing modifications. They also guide endonucleases that cleave precursors. This generates rRNAs for incorporation into ribosomes.

46
Q

what do tRNAs do?

A

transfer amino acids onto a growing peptide guided by mRNA sequence. they are ~80 bases long w extensive internal base pairing

47
Q

How are amino acids added to growing peptides by tRNA’s?

A

Anti-codon of the tRNA pairs with the mRNA in the ribosome, modifications may allow binding to multiple base in mRNA (wobble). A specific amino acid is covalently bound to the 3’-end of the tRNA allowing the tRNA to translate information encoded in the mRNA into a protein.

48
Q

Why do tRNA contain a modified based like pseudo-uridine, or deamination of A to form inosine?

A

these modifications may allow binding to multiple bases in mRNA (wobble)

49
Q

what are the 3 characteristics of how tRNA is transcribed?

A

1) tRNA are transcribed by RNA pol III
2) Transcripts are not processed at 5’ or 3’-ends (no cap or polyA tail)
3) tRNA do not contain introns.

50
Q

What is similar between the way tRNA and mRNA are transcribed?

A

Splicing is catalyzed by proteins not RNAs. tRNA precursor needs proper folding so endonuclease cuts both intron-exon boundaries following which tRNA ligase joins the exons.

51
Q

how are amino acids attached to the tRNA?

A

The amino acid is added to the 3’ end of a mature tRNA, this is catalyzed by a specific aminoacyl-tRNA synthetases for each amino acid. The reaction is ATP dependent and creates a high energy bond between tRNA and the amino acid

BIOL 361 EXAM 2 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions