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C Bio > mRNA (9) > Flashcards

mRNA (9) Flashcards

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Biology 101 flashcards
1
Q

what are the segments of the mRNA?

A
  1. 5’ cap of methylguanosine
  2. a 5’ un-translated region (5’UTR)
    a. Not converted into AA sequence
  3. a continuous sequence of nucleotides encoding a PRO
  4. an untranslated region 3’ to the “coding” region (3’UTR)
  5. tail of about 250 A nucleotides –> polyAtail
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2
Q

What segments of the mRNA are located on the 5’ of the molecule?

A

cap of methylguanosine

UTR

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3
Q

What segments of the mRNA are located on the 3’ of the molecule?

A

poly A tail

UTR

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4
Q

Heterogenous nuclear RNA

A

hnRNA
heterogenous in size & sequence
located in the nucleus
Contains intervening non-coding regions, introns which are spliced out forming the smaller cytoplasmic form

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5
Q

RNA splicing

A

removal of introns

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6
Q

What does the mature cytoplasmic mRNA contain?

A

methylguanosine cap on the 5’ end

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7
Q

What is the role of consensus sequences?

A

recruit machinery for splicing

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8
Q

snRNPs

A

snRNAs + PROs

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9
Q

spliceosome

A

complex of snRNA, hnRNA & PROs

formed as transcription occurs

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10
Q

splice donor site is __’

A

5’

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11
Q

splice acceptor site is ___ ‘

A

3’

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12
Q

U PROs

A

recognize each other & bind to their substrates by base pairing at splice consensus site using their snRNAs

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13
Q

what will effect binding of snRNP?

A

mutation of the intron

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14
Q

what are the jobs of the spliceosome?

A

matching
cutting at junctions
ligation of hnRNA

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15
Q

What is the role of U1 snRNA in intron splicing?

A

binds to the 5’ side, base pairs with snRNA

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16
Q

What is the role of U2 snRNA in intron splicing?

A

binds to a certain region, the branch

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17
Q

What is the role of U4/U6 & U5 snRNA in intron splicing?

A

bind displacing U1, spliceosome assembles

U4 will displace

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18
Q

What is the role of U6 snRNA in intron splicing?

A

binds to U2 in the complex of 3 & cuts and ligates axons together

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19
Q

What is the role of U5 snRNA in intron splicing?

A

holds 2 ends during cutting process

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20
Q

how to is binding achieved in splicing

A

with base pairing

21
Q

When does the spliceosome form?

A

when U4/U6 & U5 bind

22
Q

ribozyme

A

RNA molecule with catalytic activity

apart of the intron

23
Q

when does splicing only occur with an RNA molecule

A

some eukaryotes (protozoans)
mitochondria
chloroplasts

24
Q

RNA can serve as both:

A

info storage &

catalysts

25
Q

what is the role of the 5’ methylguanosine cap?

A

enables hnRNA of getting out of nucleus with protection from exonucleases
exporting attach to cap to transport out of the nucleus
start translation process

26
Q

5’ methylguanosine cap structure

A

inverted guanine

after synthesis, guanine is added & then methylated

27
Q

how do exonuclease attack?

A

outside inwards

28
Q

how do exonucleases attack?

A

from the middle

29
Q

mRNA processing

A

capping
splicing
tailing

30
Q

what occurs in tailing of the mRNA?

A

endonuclease cuts in the middle, ~20 bp away from the polyA signal consensus sequence
As are added (without a template) by Poly(A)polymerase

31
Q

what happens to remaining hnRNA after polyA tail is added?

A

RNA will get chopped up b/c the cap is gone
will begin to be fragmented by exonucleases
causes structure to loosen up & fall off to start again

32
Q

What causes the polymerase to stop from forming mRNA from hnRNA?

A

will lose general transcription factors

33
Q

what removes the polyA tail & where?

A

polyAribonuclease & in the cytoplasm

34
Q

what determines the half-life of an mRNA? & when is it degraded? & what attacks it?

A

the length of the RNA tail

when ~30As remain, exonuclease

35
Q

how does the polyA tail influence PRO expression? & what kind of control is it?

A

lifespan of mRNA influences the amount of PRO made –> translational level control

36
Q

what influences the half life of mRNA?

A

length of polyA tail & 3’UTR

37
Q

3’ UTR role

A

repetitive sequences that cause PROs to bind to them & protect them or recruit exnoculeases, influence the polyA tail

38
Q

what stabilizes the mRNA?

A

3’ UTR sequence that prevents polyA ribonulease activity

39
Q

what is important to the function of a PRO

A

the domain structure

40
Q

what type of PRO means that their function can be altered by alternative splicing?

A

modular PRO structure

41
Q

how does alternative splicing affect birds?

A

a single potassium ion channel in the ear can be altered many diff ways, each way changes the sensitivity to the potassium channel & changes the response to a diff pitch

42
Q

what diseases can emerge from alternative splicing?

A

Progeria –> lamin A

Tau PRO –> alzheimer’s disease

43
Q

Why is alternative splicing important in insects?

A

gender determination

the splicing out of the gene contain the stop contain producing a sex lethal PRO

males don’t do alternative splicing, females do

female has all of splice site PROs so she gets all of the exons, male doesn’t

44
Q

how do splice enhancing PROs work?

A

some splice sites are weak & cannot attract U PROs to form spliceosomes (b/c they don’t match the consensus sequence very well) causing an exon to be omitted but splice enhancing PROs recognizes the intron & restores the splicing restoring the exon

45
Q

what is normal alternative splicing?

A

enhancing PRO present

46
Q

Enhancers

A

bind to weak splice sites & guide machinery

47
Q

alternative splicing

A

splice enhancing PRO is missing, middle exon is skipped over

48
Q

importance of introns

A

allow for a variety of PRO to be derived from one gene

C Bio (30 decks)

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