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Grade 12 Biology > Transcription + Translation > Flashcards

Transcription + Translation Flashcards

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1
Q

where does transcription occur?

A

the nucleus

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2
Q

where does translation occur?

A

cytoplasm or RER

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3
Q

where does RNA processing occur?

A

the nucleus

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4
Q

gene definition

A

the stretch of DNA that is transcribed into RNA also called transcription

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5
Q

what are the main stages of transcription

A

initiation, elongation, termination

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6
Q

what is the promoter region?

A

where the RNAP first binds and RNAP starts transcribing and has the transcription start point

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7
Q

how many promoters do prokaryotes have?

A

one RNAP

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8
Q

how many promoters do eukaryotes have? Name them and what do they do

A

3:
RNAP I makes rRNA
RNAP II involves in transcription (makes mRNA)
RNAP III makes tRNA

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9
Q

Where is the promoter located?

A

upstream ofthe gene

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10
Q

what is the promoter composed of?

A

an AT rich region

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11
Q

why is the promoter composed of AT rich region

A

AT have fewer hydrogen bonds, meaning they require less energy to have

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12
Q

describe the pribnow box

A

is the AT rich region in prokaryotes that is located -10

consensus sequence: TATAAT

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13
Q

decribe the TATA box

A

the AT rich region in eukaryotes located at -15

consesus sequence: TATAAA

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14
Q

Describe the transcription initiation in prokaryotes

A
  • RNAP recognizes and binds to the promoter
  • unwind the DNA
  • begin transcription at start site
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15
Q

describe transcription initiation in eukaryotes

A

a transcription pre initiation complex is formed that consists of the following components in binding order
- transcription factors: protein that help initiate and regulate transcription
- inactive (dephosphorylated) RNAP II on promoter
- RNAP phosphorylated the C-terminal domain (CTD)
- transcription beings one the CTD on RNAP is phosphorylated

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16
Q

sense strand

A

the coding strand

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17
Q

antisense strand

A

the template and noncoding strand

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18
Q

transcript

A

newsly synthesized RNA

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19
Q

describe the transcription termination in prokaryotes

A

two inverted repeats of GC regions on DNA, once on the RNA they form complementary bonds with each other which results in a GC hairpin loop which causes the RNAP to stall, from there the adenine on DNA transcribe into uracil on RNA results in a dA/U rich region with weak interactions so RNAP stops transcribing and RNA released from RNAP

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20
Q

describe the termination process of a eukaryote in transcription

A

dephosphorylation of CTD on RNAP II which reduces rate of elongation and increases pausing

has a terminator sequence AAUAAA on the nascent RNA, which stalls/pauses RNAp II but the RNAP II can still continue for a few bases to thoushands of bases past the sequence

40-60 nucleotides downstream of terminator sequence GU righ sequence with signals the cleavage of RNA by an endonuclease

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21
Q

in what types of cells does RNA processing occur?

A

eukaryotes

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22
Q

what are the 3 types of RNA processing?

A

capping, polyadenylation, splicing

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23
Q

Describe the RNA processing capping: Where, When, Purpose, Mechanism

A

Where: 5’ end
When: con transcriptional (at the same time as others)
Purpose: protect and facilitate ribosome binding
Mechanism: addition of modeified guanine

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24
Q

Describe the RNA processing polyadenylation: Where, When, Purpose, Mechanism

A

Where: 3’ end
When: post transcriptional (after transcription)
Purpose: protect and facilitate mRNA export
Mechanism: addition of many adenine nucleotides

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25
Q

Describe the RNA processing splicing: Where, When, Purpose, Mechanism

A

Where: introns
When: co or post transcriptional
Purpose: alternatice splicing, exon shuffling
Mechanism: intron is excised

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26
Q

describe the 5’ cap

A

modified guanine added to the 5’ end that is added by capping enzyme complex to protect mRNA from degradation and signal ribosome attachment

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27
Q

what adds the adenine to the 3’ end? what does it do?

A

poly-A polymerase to protect mRNA from degradation and facilitate export of mRNA from nucleus

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28
Q

what are introns

A

INtervening sequences interspersed between exons

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29
Q

exons

A

coding sequences EXpressed

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30
Q

what is the protein component of splicing? What do they do?

A

snRNP = snRNA + protein

it binds to the splice site (snRNA is complementary to the splice site) and forms a spliceosome and exices (cuts out) the intron then rejoins the exons

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31
Q

what is the function of an intron?

A

it allows for a single gene to encode for multiple polypeptides by removing different regions to form different polypeptides (which segments are treated as exons), they have a regulatory role and occurs at the RNA level

32
Q

What are the four steps in translation initiation?

A
  1. ribosome (small subunit) finds and binds to the mRNA strand
  2. ribosome locates translation start site (AUG codon)
  3. intator tRNA binds
  4. ribosome large subunit binds
33
Q

describe step 1 of translation initiation: ribosome finds and binds to the mRNA strand in PROKARYOTES

A

the 5’ end of the mRNA transcript has a Shine-Dalgarno sequence and the rRNA on the ribosome small subunit has a complementary anti Shine-Dalgarno sequence which helps it find and bind to the 5’ end of the mRNA

34
Q

describe step 1 of translation initiation: ribosome finds and binds to the mRNA strand in EUKARYOTES

A

ribosome small subunit recognizes and binds to mRNA at 5’ cap

35
Q

what is a ribonucleoprotein composed of?

A

ribosomal RNA and a protein

36
Q

where is the ribosome made in eukaryotes?

A

nucleolus

37
Q

what are the 2 subunits of the ribosome?

A

the large subunit (60s) and the small (40s)

38
Q

what are the 4 binding sites of a ribosome?

A
  • A site, aminoacyl tRNA binding site
  • P site, peptidyl-tRNA binding site
  • E site, exit site
  • mRNA binding site
39
Q

Describe the second step of translation initiation

A

the ribosome small subunit moves along 5’ leader of mRNA until reach translation start site (start codon AUG)

40
Q

in prokaryotes what factors help ribosome small subunit find start codon?

A

initiation factors

41
Q

in eukaryotes what factors help the ribosome small subunit find the start codon? where is it

A

Kozak sequence on the mRNA

42
Q

describe step 3 of translation initiation

A
43
Q

anticodon

A

complementary sequence of a codon on tRNA

44
Q

what does tRNA do?

A

carries the amino acid to make the polypeptide chain

45
Q

what is the starting amino acid in prokaryotes?

A

fmet - formyl methionine

46
Q

what is the starting amino acid in eukaryotes?

A

met, regular methionine

47
Q

what does the A site on the ribosome do?

A

holds the aatRNA carrying the next amino acid to be added

48
Q

what does the P site on the ribosome do?

A

holds the tRNA molceule carrying the growing polypeptide chain

49
Q

what does the E site on the ribosome do?

A

where the tRNA molecules leave the ribosome

50
Q

what type of bond is formed between the amino acids on the P site and A site?

A

a peptide bond

51
Q

translocation requires energy

A
52
Q

what are the 3 main steps of polypeptide elongation?

A
  1. codon recognition
  2. peptide bond formation
  3. translocation
53
Q

describe the termination process for translation

A

a stop codon called a release factor binds to the A site, it adds a water molecule instead of amino acid to polypeptide the polypeptide in the P site is hydrolyzed from tRNA in P site and released and the translation complex disassembles

54
Q

polyribosomes

A

when 1 molecule of mRNA has multiple ribosomes simultaneously translating the mRNA

55
Q

what direction do ribosomes go in

A

from 5’ to 3’

56
Q

if the ribosome is free/unbound where are the proteins that it produces?

A

cytoplasmic proteins

57
Q

if a ribosome is bound to the ER and goes to the golgi where are the proteins it produces?

A

secretory proteins

58
Q

describe cytoplasmic proteins

A
  • water soluble
  • folds spontaneously on its own into its tertiary structure
  • but sometimes cytosol does not necesarily provide the right environment for the protein to fold
59
Q

what is the role of chaperon proteins?

A

provides the ideal microenvironment for folding and keep the cytoplasmic proteins separated from other influences in the cytosol

60
Q

describe the environment the chaperon protein provides and why it is the way it is.

A

hydrophilic since the cytoplasmic protein exists in the hydrophilic cytoplas

61
Q

describe signal sequences

A

5-30 hydrophobic amino acids at the leading end/N terminus of a polypeptide and makes the polypeptide destined for the ER aka signal peptide

62
Q

describe the stop-transfer sequence

A

it is located on the nascent polypeptide and achors into the membrane so the polypeptide does not get released into the lumen

63
Q

what does an signal recognition particle (SRP) do?

A

binds to the signal sequence stopping translation

it binds to an SRP receptor on the ER membrane bringing an entire translation complex with it and the ribosome is docked on the ER membrane

64
Q

translocon

A

similar to a channel protein in which the signal seuqnce is oriented into threading the polypeptide into the ER lumen making the SRP is released and translation resumes

65
Q

what does a signal peptidase do?

A

cleaves (like cleavage) the signal sequence

66
Q

describe the pathway of secretory proteins

A
  • the stop transfer sequence on the nascent polypeptide anchors into the membrane so that the polypeptide does not get released into the lumen
  • vesicles pinch off from ER and fuse onto the golgi with polypeptide attached to membrane
  • vesicles pinch off from golfi and exocytose to cell membrane where polypeptide becomes incorporated onto the cell surface
67
Q

name all the organelles in the endomembrane system

A
  • vesicles
  • lysosome
  • smooth endoplasmic reticulum
  • rough endoplasmic reticulum
  • golgi apparatus
68
Q

what dose a vesicle (or transport vesicle)

A

takes lipids to golgi apparatus

69
Q

what does the lysosome do?

A

contains digestive enzymes that break down cell parts or substances entering by vesicles

70
Q

what does the smooth ER do?

A

synthesizes lipids and has various other functions

71
Q

what does the rough ER do?

A

synthesezes proteins and packages them in vesicles

72
Q

what does the golgi apparatus do?

A

modifies lipids and proteins from the ER sorts and packages them in vesicles

73
Q

what are the post-translation modifications?

A
  • addition
  • removal
  • polymertization
  • folding
74
Q

describe the post translational modification addition

A

adding sugards, lipids, sulfate or phosphate groups

75
Q

describe the post translational modification removal

A

cleavage - some amino acids such as methionie or whole polypeptide chains are separated

76
Q

describe the post translational modification polymerization

A

two or more polypeptides may join together to form a protein like hemoglobin

77
Q
A

Grade 12 Biology (25 decks)

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