The flashcards below were created by user
kjel
on FreezingBlue Flashcards.
-
4 translation requirements:
- amino acids
- messenger RNA
- ribosomes
- transfer RNA
-
translation of mRNA
the biological polymerization of amino acids into polypeptide chains
-
ribosomes are made of...
- ribosomal proteins (form surface)
- ribosomal RNA (rRNA) (form core)
- also-->
- 2 sub units; small matches tRNA to codons; large forms peptide bonds
- mRNA binding site (on small sub unit),
- A, P, E (on large sub unit)
- Aminoacyl-tRNA,
- Peptidyl-tRNA
- Exit
eukaryotic larger than prokaryotic
-
polysomes (polyribosomes)
mRNAs with several ribosomes translating at once
-
Charged tRNA
tRNA is considered charged after its specified amino acid has been bonded to its 3’ end by aminoacyl tRNA synthase (one for each amino acid = 20)
-
eukaryotic pre-mRNA gets processed by...
- 5' cap w/ 7-methylguanosine
- 3' poly-A tail (polyadenylation)
- Splicing: introns excised
-
transcription begins with template binding by RNA pol at a _______.
Initiation begins when the ______ recognizes specific DNA sequences called the ______.
- transcription begins with template binding by RNA pol at a promoter. Initiation begins when the σ subunit recognizes specific DNA sequences called the promoter.--> found upstream (5') from initial transcription of gene
-
what is the direction of transcription determined by?
the orientation of the promoter
-
4 stages of transcription...
- 1. Binding of RNA pol (@ promoter) and local DNA unwinding
- 2. Initiation of RNA synthesis
- 3. Elongation of RNA
- 4. Termination of RNA synthesis
-
σ factor
- In bacteria,
- a subunit of RNA pol, recognizes promoter
- σ factor detaches after transcription has initiated
-
polycistronic mRNA
-->what are their units called?
- in bacteria, mRNA that can encode more than one protein within the same transcript.
- units: operons
- (eukaryotes have monocistronic mRNA)
-
Transcription in eukaryotes...differences
- occurs in nucleus under the direction of three different forms of RNA polmRNA moves out of the nucleus into the cytoplasm for translation
- Euk. RNA pol rely on transcription factors to scan and bind to DNA
- In addition to promoters, other control units called enhancers and silencers also control transcription regulation
-
RNA pol II
determines where it should bind to DNA and where it begins copying DNA into RNA
-
TATA box
core promoter element that binds TATA-binding protein of transcription factor TFIID and determines the start site of transcription
-
general flowchart of transcription factors and RNA pol II...
- D binds to TATA box → others bind →
- RNA pol II binds → phosphorylation → transcription begins
-
introns are spliced out of euk. pre-mRNA by the _______
- spliceosome
- snRNPs, an important component of spliceosomes, are involved in excision
- (small nuclear ribonucleoproteins)
- Catalytic RNAs are called “ribozymes.”
-
alternative splicing
- 1 kind of pre-mRNA → different version of mature mRNA
- Each mRNA transcript still gives rise to one polypepti
-
in bacteria the start codon codes for this modified amino acid
formylmethionine (fmet)
-
termination codons
- UAA, UAG, UGA
- **if mutation one of these then nonsense mutation
-
modified bases on tRNA
- Inosinic acid (I)
- Pseudouridylic acid (ψ)
- -==- aid in wobble by being able to pair with more than one ribonucleotide
-
3 phases of translation
- initiation
- elongation
- termination
-
ribosome binding site of bacterial mRNA
- Shine-Delgarno sequence
- -where rRNA small subunit binds to mRNA
- --small subunit binds to initiation factors (IFs)
- --then tRNA fMet binds to P site and mRNA binds
- --then large subunit associates
-
elongation during translation flowchart
- initial P-site bonding of tRNAmet
- elongation continues w/ charged tRNA binding to A-site
- large subunit catalyzes bond b/t P-site tRNA and its amino acid (peptidyl transferase)
- peptide bond formed b/t hydrolyzed aa chain and incoming A-site tRNA aa
- discharged tRNA translocated to E-site and ejected
-
ribosome binding site of eukaryotic mRNA
- Kozak sequence
- increases efficiency of translation by interacting with initiator tRNA
-
base-pair substitutions/insertions or deletions create 4 types of mutations
- missense - different protein
- nonsense - stop
- silent - no change
- frameshift
|
|