Explained the way in which the information encoded in the DNA was expressed in the cell
2
New cards
Francis Crick
Who proposed the central dogma and wobble hypothesis?
3
New cards
codon
Sequence of three bases that specifies a single amino acid
4
New cards
unambiguous, redundant, specific start/stop signals, no punctuation, nearly universal
5 characteristics of the genetic code
5
New cards
wobble hypothesis
\-The base at the 5' end of the anticodon (complementary to the base at the 3' end of the codon, i.e. the third letter) is not as constrained as the other two
\-Therefore, certain tRNA molecules can pair with more than one codon
6
New cards
AUG
What is the start codon?
7
New cards
nonsense
What type of codons are stop codons?
8
New cards
missense mutations
mutations that change the amino acid coded
9
New cards
nonsense mutations
mutations that change sense codon to nonsense and prematurely stop translation
10
New cards
Transcription
The process of synthesizing an RNA copy of a section of DNA
11
New cards
template strand
The DNA strand that is copied by RNA polymerase
12
New cards
complementary
The nontemplate strand is _____ to the template strand
13
New cards
gene
In transcription, template and nontemplate strands are _____ specific
14
New cards
DNA template, Ribonucleose Triphosphates, RNA polymerase, Mg++
What does transcription require?
15
New cards
primer
unlike DNA replication, transcription does not require ____
16
New cards
5â, 3â
RNA is synthesized from __ to __
17
New cards
3â, 5â
RNA polymerase moves along the template from __ to __
18
New cards
initiation, elongation, termination
What are the 3 stages of transcription?
19
New cards
core enzyme
responsible for polymerization activity during initiation
20
New cards
holoenzyme and sigma
What is needed in addition to the core enzyme to ensure transcription begins at the correct location?
21
New cards
promoter
A specific regulatory nucleotide sequence in the DNA to which RNA polymerase binds in order to initiate of transcription
22
New cards
upstream
opposite of the transcription start site to the direction RNA polymerase moves
23
New cards
RNA polymerase initiates transcription randomly
what happens if sigma is absent?
24
New cards
\-10 region and -35 region
What are the 2 critical conserved sequences in ecoli promoter?
25
New cards
downstream
Base pair substitutions or deletions in critical conserved regions results in either diminished or enhanced transcription of the gene _______ from them
26
New cards
cis
Promoter sequences are **_____ acting** regulatory sequences
27
New cards
consensus sequence
\-The most prevalent sequence at a specific location
\-Identified by sequencing the same region of a large number of genes and identifying the most common nucleotide at each position
28
New cards
yes
Do cis-acting regulatory sequences need to be directly adjacent to the parts of the DNA that they are regulating?
29
New cards
holoenzyme, open promoter complex, template
In initiationâŚ
â˘The _______ binds to the promoter
â˘The DNA double helix opens up and an **____________** is formed
â˘This exposes the _________
30
New cards
ribonucleoside triphosphate
The first _______________, complementary to the nucleotide at the transcription start site, is brought in and bound to the template
31
New cards
5â to 3â phosphodiester
what type of bonds are formed between nucleotides
32
New cards
8nt
Since the first few attempts at polymerization tend to be abortive, at what length is the dna/rna hybrid typically stable?
33
New cards
sigma
what is released from the holoenzyme once the stable 8nt length is reached?
34
New cards
core enzyme, 5â to 3â, unwound
In ElongationâŚ
â˘The _________ slides along the DNA and catalyzes the denaturation of the two DNA strands
â˘RNA polymerization takes place in the _______ direction
â˘A short stretch of DNA is kept ________ as transcription continues
35
New cards
10-12
within the unwound region, how many bp of RNA are H-bonded to the DNA in a RNA-DNA hybrid?
36
New cards
specific DNA sequences, stops, released, released
TerminationâŚ
â˘Indicated by ___________ which signal that:
â˘RNA synthesis ____
â˘RNA molecule is _________ from the DNA
â˘RNA pol is _________ from the DNA
37
New cards
38
New cards
rho-independent and rho-dependent
what are the 2 kinds of termination signals in prokaryotes?
39
New cards
rho independent terminators
* Sequence w/ two-fold symmetry followed by series of around 6 AT bp * Causes hairpin loop ->stalls RNA pol
40
New cards
rho dependent terminators
* Still have 2 fold symmetry * Lack AT string * So RNA wont fall off after hairpin loop * Need accessory Rho to pull RNA pol off
41
New cards
polycistronic RNA
RNA that consists of more than one gene, only in prokaryotes
42
New cards
Monocistronic RNA
RNA that consists of only one gene, all eukaryotic RNA
43
New cards
prokaryotic because there is no nuclear envelope
In which type of cell can transcription and translation occur at the same time, why?
44
New cards
chromatin remodeling, 3 different RNA polymerases, more complex regulation, RNA polymerases donât bind to ânakedâ promoters
What are some differences in eukaryotic vs prokaryotic transcription?
What are the 4 major classes of cis acting elements in eukaryotes?
46
New cards
core promoter elements
* \~-40 to \~+40 * Determine where RNA polymerase binds and where transcription is initiated * Not responsible for differential gene expression * Contain some initiator element, tata box, BRE (B recognition element)
47
New cards
proximal promoter elements
* Within 100 nt upstream of +1 * Effect efficiency with which RNA pol binds * Increase basal level of transcription * Ex: GC and CAAT boxes * Mutations in these sequences drastically reduce transcription
48
New cards
enhancer and silencer elements
* Turn genes on and off when they are needed * Responsible for tissue specific/temporal patterns of expression * Act at a distance to modular transcription * Can be thousands of bp up or downstream of +1
49
New cards
by binding to proteins
how are cis-acting elements turned on and off
50
New cards
by the transcription factors bound to them.
How do eukaryotic RNA polymerases recognize promoters?
51
New cards
general transcription factors
* Bind to core promoter elements * Bind to all promoters recognized by rna pol II * Must always be bound for transcription to occur
52
New cards
specific transcription factors
* Transcriptional activators & repressors * Bind to specific sequences * Regulate expression of specific genes and tissue specific/temporal patterns of gene regulation
53
New cards
transcriptional activators
â˘Bind to proximal promoters and/or enhancers and thereby promote RNA polymerase binding
54
New cards
transcriptional repressors
â˘Inhibits transcription by blocking the binding of activators or general transcription factors
55
New cards
eukaryotic
What type of RNA is processed following transcription?
56
New cards
5â capping, poly A tail addition, splicing
what does the processing of mRNA include?
57
New cards
5â capping
* Occurs early during rna synthesis (chain \~25 nt) * involves addition of 7-methlyguanosine residue * By 5â to â5 triphosphate bond * Essential for⌠* Subsequent processing * Transport to cytoplasm * Attachment to ribosome
Protection to degradation
58
New cards
creates a 5â to 5â bond that canât be broken
how does 5â capping help prevent degradation?
59
New cards
poly A tail addition
* Genes transcribed by RNA pol II donât have specific termination signal, most have polyadenylation signal
* Cleavage at polyadenylation site * Addition of adenylic acid residues by poly A polymerase * Essential for⌠* Transport to cytoplasm * Protection from degradation
60
New cards
exons
coding/expressed sequences
61
New cards
introns
â˘Noncoding (intervening) sequences
â˘Must be removed from the pre-mRNA
62
New cards
splicing
* Eukaryotic transcripts contain long sequences of noncoding RNA * Removes introns and brings exons together
63
New cards
I and II
which groups of introns are self splicing?
64
New cards
no
are nuclear pre-mRNA introns self splicing?
65
New cards
5â -GU, 3â -AG, A branch
Nuclear pre-mRNA intronsâŚ
* Usually begin w/ ___ and end w/ __ * Include _______ site
66
New cards
Lariet
what model is used to describe nuclear pre-mRNA splicing
67
New cards
spliceosomes
Where does splicing occur?
68
New cards
alternative splicing
What is assembling exons and introns in different orginizations to generate different products called?