Transcription and translation Flashcards
1
Q
The central dogma describes
a …
A
…flow of information in an
organism
2
Q
How many nucleotides in DNA and RNA?
A
4
3
Q
DNA is …
A
…double stranded
4
Q
RNA is …
A
…single stranded.
5
Q
flow of information in an organism?
A
DNA -> RNA -> Protein
6
Q
How does DNA flow into RNA?
A
Transcription of genes into mRNA
7
Q
How does RNA flow into proteins?
A
Translation of mRNA.
8
Q
What is a gene?
A
- the DNA sequence that is translated into a protein
- the open reading frame (ORF) and the control region of the gene including its promoter
9
Q
genes are not separate from the rest of the DNA that they inhabit – they are part of the …
A
…DNA sequence
10
Q
Genes are information units…
A
…which allow the production of proteins
11
Q
Eukaryotes tend to have more genes than …
A
…prokaryotes
12
Q
Eukaryotes tend to have more genes than prokaryotes but there is little correlation between our own conception of …
A
…‘higher’ organisms and the number of genes
– all multi-cellular organisms have similar numbers of genes.
13
Q
there can be little correlation between the size of the genome and the…
A
…number of genes.
14
Q
DNA is folded in the nucleus into …
A
…higher structures by interaction with histone proteins.
This makes the DNA highly packaged
15
Q
genes are encoded on …
A
…either strand of the double helix
16
Q
genes are encoded on either strand of the double helix – in general these do not overlap in eukaryotes but often do in…
A
…viral genomes where there are space constraints
17
Q
RNA molecules are transcribed so that the RNA molecule is complementary to the sequence of the …
A
…antisense or template strand
18
Q
RNA molecules are polymerised by the addition of…
A
…ribonucleotides to a growing strand
19
Q
RNA molecules are polymerised by the addition of ribonucleotides to a growing strand
– the addition of an individual nucleotide is determined by the …
A
…base present on the antisense strand of the gene – where the antisense strand has a C then a G is added to the growing strand, where there is an A then a U is added and so on
20
Q
transfer RNAs are not …
A
…translated
21
Q
Transfer RNAs act as…
A
…adaptor molecules between base pairing via their anticodon and the construction of proteins as they are attached to a specific amino acid
22
Q
the 3D structure of rRNA provides …
A
…binding sites for 3 tRNA molecules (complete with their amino acids) and the mRNA in the ribosome
23
Q
because individual nucleotides are able to form ‘base pairs’ then whole RNA molecules fold up into a …
A
…three dimensional structure (as with proteins.
24
Q
because individual nucleotides are able to form ‘base pairs’ then whole RNA molecules fold up into a three dimensional structure (as with proteins) due to …
A
…intramolecular forces (in this case hydrogen bonds)
– the three dimensional shape is related to their function.
25
Transcription is controlled by ...
...DNA-protein interaction
26
in order for a gene to be transcribed there is a requirement that the proteins involved in transcription are able to ...
...interact with DNA
27
in order for a gene to be transcribed there is a requirement that the proteins involved in transcription are able to interact with DNA
- without this interaction they would not be able to...
...‘read’ the DNA sequence and transcribe the gene.
28
DNA binding proteins have conserved ...
... 'motifs'
29
DNA binding proteins have conserved ‘motifs’
one of the most common is the ...
...helix-turn-helix motif
30
In helix-turn-helix motifs an alpha-helix is positioned into the...
...major groove of DNA by intramolecular forces between amino acids and nucleotides
31
Purpose of recognition motifs?
recognises particular sequence in the DNA molecule
32
Transcription requires ...
...RNA polymerase
33
RNA polymerases are enzymes which ...
...catalyse the formation of RNA polymers in a similar way to DNA polymerases acting in replication.
34
RNA polymerase requires a ...
...dna template
35
RNA polymerase requires a DNA template – it consists of...
...multiple protein subunits which enable it to unwind DNA, denature the double strands, add ribonucleotides to a growing chain and proofread the transcripts it is producing.
36
CDK 8 is a component of the ...
... mediator complex
37
In prokaryotes, RNA polymerase requires an associated protein (sigma factor) to recognise ...
...where transcription begins
38
associated protein is also known as...
...sigma factor
39
as RNA polymerase begins to produce mRNA...
...sigma factor is released
40
as RNA polymerase begins to produce mRNA sigma factor is released – the polymerase then progresses along the gene until it reaches a ...
...termination signal where it is released
41
In prokaryotes, promoter sequences are ...
... heterogenous
42
In prokaryotes, promoter sequences are heterogenous, and therefore have different...
...binding affinities for sigma factor.
43
In prokaryotes, promoter sequences are heterogenous, and therefore have different binding affinities for sigma factor.
- However a general [...] sequence can be read.
However a general consensus sequence can be read.
44
In prokaryotes, promoter sequences are heterogenous, and therefore have different binding affinities for sigma factor.
- However a general consensus sequence can be read.
- The consensus sequence is...
1) TTGACA at a position 35 nucleotides upstream of the transcription start site.
2) TATAAT at a position 10 nucleotides upstream of the start site.
45
Terminator sequences are even more...
...heterogenous.
46
Terminator sequences are even more heterogenous but always contain a sequence which will cause the RNA to form a ...
... hairpin structure which causes the polymerase to be dislodged.
47
Promoters for RNA polymerase II are heterogenous and typically include...
... two or three of the four consensus sequences shown below.
48
RNA polymerase needs to be directed to the start of genes that the cell requires transcribing
this is accomplished by ...
...sequence-specific binding of basal transcription factors TFIID, A, B, F, E and H.
49
TFIID includes...
...TATA-binding protein (TBP)
50
TFIID includes TATA-binding protein (TBP) which recognises the ...
...TATA box which is located ~25 bases upstream of the transcription start site
51
binding of the basal factors recruits ...
...RNA polymerase
52
binding of the basal factors recruits RNA polymerase and ...
...transcription can begin
53
The mRNA molecule produced by transcription is complementary to the ...
...template/antisense strand of the gene and has the same sequence as the sense strand
54
in the mRNA T (in the gene) is replaced with ...
... U
55
mRNA transcripts contain both ...
...coding and non-coding sequences (5’ UTR and 3’UTR)
56
in eukaryotes mRNA molecules are processed after completion of transcripts by addition of a...
... 5’ cap and a poly-A tail.
57
Eukaryotic genes have ...
...introns and exons
58
whilst prokaryotic genes tend to be quite simple, eukaryotic genes usually have a complex structure of ...
...introns and exons
59
The exons are...
...coding sequences.
60
The introns are...
...non coding
61
introns need to be removed from...
... the immature mRNA transcript before translation can take place
62
a mixture of small nuclear RNA molecules (snRNA) and proteins are responsible for ...
...the excising of introns and joining together the 3’ and 5’ ends of exons to form the mature transcript.
63
a mixture of small nuclear RNA molecules (snRNA) and proteins are responsible for the excising of introns and joining together the 3’ and 5’ ends of exons to form the mature transcript.
This only happens in...
...eukaryotes
64
sometimes the exons of genes with multiple introns can be...
...spliced together in different ways – (alternative splicing)
– this means that the coding sequence of the transcripts can differ and results in different proteins which may be involved in different processes
65
because prokaryotes have their genomic DNA naked in the cytoplasm (no nucleus) and doesn’t require polyadenylation or intron removal,...
...transcription and translation are coupled
66
because the eukaryotic cell has a nucleus – mRNA needs to be transported into the...
...cytoplasm to be translated into protein by the ribosome
67
mRNAs are marked for export by the interaction of specific proteins:
cap-binding protein
poly-A-binding protein
exon junction complex (EJC)
68
there are 64 possible ways of writing the four letters A, C, G and U – but only 20 amino acids (plus stop signals) – the genetic code therefore contains ...
... redundancy
69
there are 64 possible ways of writing the four letters A, C, G and U – but only 20 amino acids (plus stop signals) – the genetic code therefore contains redundancy – some amino acids are encoded by...
... several codons
70
Stop translation is encoded by...
... 3 stop codons
– UGA, UAG and UAA
71
Protein sequence is determined by...
... a 3 letter code.
72
The transcript is read by the ribosome as a ...
...set of instructions for adding amino acids to a growing polypeptide (protein) chain
73
the ribosome reads ...
...triplets that encode different amino acids
74
each transcript has three separate...
...reading frames
75
each transcript has three separate reading frames but only one is used to ...
...translate the protein
76
all proteins are initiated with ...
...AUG which codes for methionine
77
In prokaryotes mRNA is positioned correctly by the...
...RNA of the ribosome base pairing with a short DNA sequence on the 5’ UTR of the mRNA
78
In prokaryotes mRNA is positioned correctly by the RNA of the ribosome base pairing with a short DNA sequence on the 5’ UTR of the mRNA – this is called the ...
...Shine-Dalgarno Box
79
mRNA has ...
...3 possible reding frames
80
Translation occurs via ...
...codon/anticodon base pairing
81
translation occurs as ...
...specific tRNA molecules carrying the correct amino acid
- interact by RNA/RNA base paring via the codon on the mRNA molecule and the anticodon on the tRNA molecule
82
ribosomes are a complex mixture of ...
...RNA molecules and proteins
83
the three dimensional shape created by the RNA and protein molecules provide the...
...catalytic site for translation
84
the ribosome contains ...
...three binding sites for tRNA molecules
85
the ribosome contains three binding sites for tRNA molecules –
...the A site (aminoacyl tRNA), the P site (peptidyl tRNA) and the E (exit) site
86
the ribosome moves along the message with...
...tRNA molecules moving between the three sites before exiting the ribosome
87
What are initiation factors ?
Initiation factors (IF) are proteins that recruit mRNA molecules and tRNA carrying formylmethionine (fMet) to the P site of the small subunit of the ribosome
88
following GTP hydrolysis the large ribosomal subunit associates with the ...
...translation initiation complex and elongation begins as the next tRNA joins at the A site
89
The polypeptide chain is formed through ...
...the repeated cycling of tRNA binding to the A site, catalysis of the peptide bond between amino acids, and ribosome translocation.
90
The incoming tRNA associates with ...
...the ribosome along with EF-Tu
91
GTP bound anticodon/codon pairing causes a...
...conformational shift in the ribosome which activates its GTPase activity and GTP hydrolyses and EF-Tu dissociates
92
the ribosome itself (without protein) catalyses the formation of the ...
...peptide bond (ribozyme)
93
translocation occurs by binding of ...
...EF-G and hydrolysis of its associated GTP.
94
peptide bonds are formed by a ...
...condensation reaction – water is released
95
peptide bonds are formed by a condensation reaction – water is released
no ATP or GTP hydrolysis is needed for the reaction to occur as it is ...
...energetically favourable
96
polypeptide chains grow in...
...one direction (N to C)
97
the amino-(N)-terminal of the protein is ...
...synthesised first and the carboxy-(C)-terminal last
98
Termination of translation occurs when the ...
...ribosome reaches one of three stop codons (UAG, UAA or UGA)
99
Termination of translation occurs when the ribosome reaches one of three stop codons (UAG, UAA or UGA)
- at this point rather than another tRNA molecule base pairing with the codon there is an interaction with a ...
...protein (release factor) that recognises the stop codon
100
The binding of release factor alters ...
...the peptidyltransferase activity of the large ribosomal subunit and causes it to add a water molecule to the carboxy-terminal of the polypeptide
101
The binding of release factor alters the peptidyltransferase activity of the large ribosomal subunit and causes it to add a water molecule to the carboxy-terminal of the polypeptide
- The ribosome...
...translocates and dissociates from the mRNA and the polypeptide
102
Many ribosomes attach to ...
... one mRNA
103
in order to increase the speed at which proteins are produced in the cell many individual ribosomes associate with ...
...one message so that many polypeptides are being produced simultaneously
