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IMS > MOLECULAR BIOLOGY OF THE GENE > Flashcards

MOLECULAR BIOLOGY OF THE GENE Flashcards

1
Q

what processes occur in the nucleus?

A

transcriptional control

processing control

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2
Q

what processes can gene expression be regulated?

A

transport control, translational control, mRNA degradation control, protein degradation control

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3
Q

what is transcriptional control?

A

t

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4
Q

what are interim regions?

A

i

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5
Q

what is ‘junk’ DNA needed for?

A

needed for organism plasticity, control of gene expression

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6
Q

describe the gene structure

A

Promoter
Transcriptional ‘start’ and ‘stop’ signal
Exons and introns
Upstream regulatory regions

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7
Q

what does the promoter do?

A

stitches a gene on

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8
Q

why aren’t genes all expressed infall cells at the same time?

A

some genes may be expressed in response to an external stimulus, others during a particular point in the cell cycle, development etc. (timing is important)

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9
Q

How does a cell keep control over which genes are expressed or not?

A

the promoter

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10
Q

what are transcriptional activators?

A

t

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11
Q

what is gene expression driven by?

A

RNA polymerase II

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12
Q

why are transcription factors needed?

A

In order for a gene to be expressed (switched on) a number of DNA-binding proteins TF bind in and around promoter region

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13
Q

how is gene expression fine-tuned?

A

via the binding of other DNA-binding proteins to distal regions termed upstream enhancer sequences

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14
Q

what is open chromatin?

A

o

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15
Q

what do activators do?

A

Activators bind

to enhancer sequence and increase expression significantly than without them (basal/low expression)

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16
Q

what does transcription create?

A

mRNAs, tRNAs and rRNA

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17
Q

what produces mRNAs, tRNAs and rRNA?

A

enzyme RNA polymerase

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18
Q

what is RNA polymerase I?

A

responsible for the production of the large ribosomal RNA

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19
Q

what is RNA polymerase II?

A

responsible for the production of mRNA

20
Q

what is RNA polymerase III?

A

responsible for the production of tRNA and the small ribosomal RNA molecules

21
Q

how does RNA polymerase bind to promoter?

A

RNA p molecules collide randomly with the DNA in the nucleus and bind with specific DNA sequences called promoters, the TATA sequence/box

22
Q

what does RNA polymerase open?

A

opens up a short length of the DNA double helix exposing a specific section of DNA on each strand.

23
Q

what are the 2 types of transcriptional repressors?

A

Interacts with activator - binding site next to activator - blocks function
Overlapping binding sites (activator, repressor) - stops activator from binding

24
Q

what is the 5’ end of the mRNA molecule capped by?

A

addition of methylated G nucleotide

3’ end is cleaved at a specific site and a poly – A tail added

25
Q

how is methylated G nucleotide added to 5’ end?

A

by removal of a phosphate by a phosphatase

addition of a GMP via a guananyl transferase addition of a mythyl group via a methyl transferease

26
Q

what are introns?

A

non coding regions

27
Q

what are exons?

A

coding regions

28
Q

how are introns removed?

A

by RNA splicing

29
Q

what is RNA splicing ?

A

s

30
Q

what is alternative splicing?

A

a

31
Q

what is the 1st AA in a polypeptide?

A

AUG (methionine) -start codon

32
Q

what is translational control?

A

t

33
Q

how does translational control occur?

A

mRNA associates with ribosomes which translate the RNA sequence into a polypeptide chain (protein)
Many ribosomes attach to each mRNA (multiple bubbles)

34
Q

what is the purpose of the half-life of mRNA?

A

another way in which the cell can regulate gene expression levels

35
Q

how does translational initiation occur?

A

an initiator tRNA carrying a methionine associates with a small ribosomal unit in association with eukaryotic initiation factor 2 ( eIF2).

36
Q

what occurs after tRNA binds to eIF2?

A

The small ribosomal unit recognises the a 5’ end of a mRNA capped with two additional initiation factors eIF4G and eIF4E, and scans along the mRNA for a start codon (AUG), which then allows the large subunit bind.

37
Q

what is stage 1 of translational elongation?

A

An aminoacyl – tRNA binds to the A site and the tRNA molecule at the E site is released

38
Q

what is stage 2 of translational elongation?

A

Carboxyl end of the polypeptide chain is uncoupled from the tRNA in the P site and joined by a peptide bond to the AA attached to the new tRNA molecule in the A site via a peptide transferase enzyme.

39
Q

what is stage 3 of translational elongation?

A

Large ribosomal sub unit steps one codon along the mRNA

40
Q

what is stage 4 of translational elongation?

A

Small ribosomal subunit steps one codon along so that the new peptidyl –tRNA in the A site moves to the P site as and the tRNA that occupied the P site of the ribosome moves 1 codon along the mRNA molecule and becomes the new E –site. This generates a new A site.

41
Q

what is translational elongation driven by?

A

Elongation factors EF1 and EF2

42
Q

what is translational termination?

A

t

43
Q

what occurs in translational termination?

A

Protein synthesis stops when the ribosome encounters a stop codon (UAA, UAG, UGA). Cytoplasmic release factors bind to the stop codon and free the carboxyl end of the growing polypeptide chain.

44
Q

what is the one gene-one protein hypothesis?

A

o

45
Q

what are isoforms?

A

Alternative mRNAs of a single gene (e.g. Casp8)

IMS (52 decks)

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