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Cell Biology and Genetics > Gene expression > Flashcards

Gene expression Flashcards

1
Q

What is transcription?

A

Producing mRNA using DNA

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2
Q

Where does transcription occur?

A

Nucleus

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3
Q

What are the stages of transcription?

A

Inititation

Elongation

Termination

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4
Q

What happens in initiation of transcription?

A

Transcription factor binds to promoter site

RNA polymerase is recruited

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5
Q

What is a common sequence in the promoter site of genes in eukaryotes?

A

TATA

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6
Q

What is the base in front of RNA polymerase marked as?

A

+1

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7
Q

What is the direction of the +1 base called?

A

Downstream

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8
Q

What direction does RNA polymerase move along the DNA strand in?

A

3’ to 5’

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9
Q

What makes RNA polymerase move along the DNA strand 3’ to 5’?

A

The binding of the transcription factor sets the direction

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10
Q

What happens in elongation of transcription?

A

RNA polymerase reads DNA strand 3’ to 5’
forms pre-mRNA 5’ to 3’

RNA processing

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11
Q

What is the DNA strand that RNA polymerase reads called?

A

DNA template strand/non-coding strand

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12
Q

What reaction occurs repeatedly in elongation of transcription?

A

(rNMP)n + rNTP —–> (rNMP)n+1 + PPi

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13
Q

What is the purpose of RNA processing?

A

Convert pre-mRNA into mature mRNA

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14
Q

What are the different processes involved in RNA processing?

A

Capping

Tailing

Splicing

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15
Q

What happens in capping?

A

At 5’ end of pre-mRNA

methylated guanine is added by 5’-5’ linkage

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16
Q

What is the purpose of capping?

A

Protect mRNA against degradation by exonucleases

Role in translation???????

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17
Q

What happens in tailing?

A

At 3’ end of pre-mRNA

many A bases are added on

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18
Q

What is the enzyme repsonsible for tailing?

A

polyA polymerase

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19
Q

What is the purpose of tailing?

A

Protect mRNA against degradation by exonucleases

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20
Q

What happens in splicing?

A

Introns are splices out of pre-mRNA

exons are joined together

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21
Q

What enzyme is responsible for splicing?

A

Spliceosome enzyme complexes

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22
Q

What is alternative splicing?

A

Refers to how some introns can be kept, some exons removed
or exons joined together in different order
to create a new protein

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23
Q

What are introns?

A

Base sequences that are not expressed

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24
Q

What are exons?

A

Base sequences that are expressed

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25
What happens in termination of transcription?
Termination sequence in pre-mRNA is recognised | cleaved by endonuclease
26
What is the name of the DNA strand that mRNA resembles?
Coding strand
27
Where does translation occur?
Cytoplasm
28
What organelle is responsible for translation?
Ribosomes
29
What is a polyribosome?
Multiple ribosomes translating mRNA at same time
30
What are ribosomes made up of?
rRNA Proteins
31
What type of ribosome is present in prokaryotes? What are its subunits?
70S ribosomes 50S and 30S subunits
32
What type of ribosome is present in eukaryotes? What are its subunits?
80S ribosomes 60S and 40S subunits
33
What are the types of RNA?
ribosomal RNA, rRNA messenger RNA, mRNA transfer RNA, tRNA
34
Are there more types of mRNA or tRNA or rRNA?
More types of mRNA then tRNA least types of rRNA
35
Are there more copies of mRNA or tRNA or rRNA?
More copies of tRNA then rRNA least copies of mRNA
36
What are the features of the genetic code?
Triplet code Degenerate Non-overlapping
37
What is the triplet code?
3 nucleotide bases code for 1 amino acid
38
What is the adapter molecule of the genetic code?
tRNA
39
What is meant by the genetic code being degenerate?
More than one triplet code | can all code for the same amino acid
40
What is meant by the genetic code being non-overlapping?
Each base belongs to one triplet code only | not more than one
41
5' to 3' mRNA produces a polypeptide chain in what order?
N to C
42
What is the structure of tRNA?
Clover leaf shape Stem loops Anti-codon
43
What are stem loops?
Anti-parallel RNA Base pairs formed in the middle
44
What is an anti-codon?
Three bases at a specific point on the tRNA molecule
45
What does the anticodon do?
Recongises mRNA codon with complementary base sequence | base pairs form
46
How do some mRNA codons code for the same amino acid?
Third base in anticodon/mRNA codon is wobble base | can form base pairs with multiple bases
47
What may be at the 3' end of the tRNA molecule?
Amino acid
48
What is tRNA called when there is no amino acid at the 3' end? And when there is an amino acid?
No amino acid - uncharged tRNA Amino acid present - amino acyl tRNA
49
What is amino acid activation?
Refers to adding amino acid to tRNA molecule 3' end
50
What happens in amino acid activation?
ATP is hydrolysed to release energy | this energy is used to combine amino acid to tRNA 3' end
51
What is the enzyme responsible for amino acid activation?
Amino acyl tRNA synthetase
52
What are the stages of translation?
Inititation Elongation Termination
53
What happens in initiation of translation?
Ribosome recruited to 5' cap of mRNA Methionyl tRNA recruited to 5' cap
54
How is the ribosome recruited to the 5' cap of mRNA in initiation of translation?
Requires energy
55
What does methionyl tRNA recognise?
Start codon AUG
56
What happens in elongation of translation?
Ribosome moves along mRNA tRNA molecules enter and leave ribosome Polypeptide chain grows
57
What direction does the ribosome move along the mRNA?
5' to 3'
58
Where do tRNA molecules leave the ribosome from?
P site
59
Where do tRNA molecules enter the ribosome into?
A site
60
How does the polypeptide chain grow in elongation of translation?
Peptidyl transferase moves amino acid from tRNA in P site to tRNA in A site forms peptide bond between the two and hence a polypeptide chain
61
What is required for elongation of translation?
Requires energy
62
What happens in termination of translation?
Stop codon enters A site | polypeptide chain is hydrolysed off tRNA at its C terminus
63
What does UTR stand for?
Untranslated region
64
Where are UTRs located?
5' and 3' end of mRNA
65
What is meant by a gene being expressed?
Gene is switched on | the protein it codes for is produced
66
Why are there many types of mRNA?
Because there are lots of genes Alternative splicing
67
Why are there few copies of mRNA?
Because many ribosomes can translate one mRNA molecule producing lots of protein molecules from it
68
Why are there few types of rRNA?
All have same function

Cell Biology and Genetics (32 decks)

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