Lesson 5 - RNA Translation Flashcards
the process in which a sequence of nucleotide triplets in a messenger RNA give rise to a specific sequence of amino acids during the synthesis of a polypeptide chain or protein
RNA translation
Ribosomes translate the genetic message of mRNA into ____
Proteins
The mRNA is translated 5’→3’, producing a corresponding _____ → _____ polypeptide
N-terminal
C-terminal
Amino acids bound to tRNAs are inserted in the proper sequence due to (2)
Specific binding of each amino acid to its tRNA.
Specific base pairing between the mRNA codon and tRNA anticodon
Translational Machinery (4)
mRNAs
tRNAs
Aminoacyl tRNA synthetase
Ribosome
Provides an intermediate that carries the copy of DNA sequence that represents protein
Messenger RNA (mRNA)
Protein coding region of mRNA is composed of a contiguous, non- overlapping string of codons called _____
Open Reading Frame (ORF)
the site of attachment of the specific amino acid
Acceptor ARM
involved in binding of the aminoacyl-tRNA to the ribosomal surface at the site of protein synthesis
Ribothymidine Pseudouridine Cytidine ARM
recognition of a given tRNA species by its proper aminoacyl-tRNA synthase
D ARM
(2) attachments of amino acids to RNA
Adenylation
Charging
Provide specificity in joining amino acids to their RNAs
Amino Acyl tRNA Synthetase
It directs the synthesis of proteins
Ribosome
contains the peptidyl transferase center which is responsible for the formation of peptide bonds
Large subunit
contains the decoding center in which charged tRNAs read or decode the codons of mRNA
Small subunit
undergo association and dissociation during each cycle of translation
Large subunit and small subunit
Prokaryotic Ribosome = ___S
Eukaryotic Ribosome = ____S
70; 80
An mRNA bearing multiple ribosome is known as ____ or ____
Polyribosome; polysome
binding site for the first aminocylated tRNA
A-site
binding site for the first peptidyl tRNA
P-site
binding site for the first uncharged tRNA
E-site
Large subunit has an exit channel for ____
Newly synthesized polypeptide chain
ordered series of three nucleotides specific for amino acids
Codon
last codon of an ORF at the 3’end which define the signal termination of protein synthesis
Stop codon
Features of Genetic Code (5)
Degenerate
Unambiguous
Non-overlapping
Not punctuated
Universal
Feature of Genetic Code
The reading of the genetic code during the process of protein synthesis does not involve any overlap of codons
Non-overlapping
Feature of Genetic Code
The code is the same in all organisms from viruses and bacteria to humans with few exceptions
Universal
Steps of RNA Translation (3)
Initiation
Elongation
Termination
The initiator tRNA is charged with with ____
Methionine
(3) key events for correct addition of each amino acids
Correct aminoacyl-tRNA is loaded to the A site of the ribosome as dictated by the A site codon
Peptidyl transferase reaction
Translocation of peptidyl tRNA from A site of ribosome to the P site of ribosome
Stop codons are recognized by proteins called ____
Release factors (RF)
(2) classes of RF
Class 1 RFs
Class 2 RFs
recognize stop codon and trigger the hydrolysis of peptide chain from the peptidyl tRNA
Class 1 RFs
stimulate the dissociation of class 1 RFs from the ribosome after the release of polypeptide
Class 2 RFs
UGA
Universal Code and Unusual Code
Stop; Trp
CUG
Universal Code and Unusual Code
Leu; Thr
UAA, UAG
Universal Code and Unusual Code
Stop; Gln
UGA
Universal Code and Unusual Code
Stop; Cys
Occurrence in UGA
Mycoplasma
Spiroplasma
Mitochondria of many species
Occurrence in CUG
Mitochondria in yeasts
Occurence in UAA and UAG
Acetubularia
Tetrahymena
Paramecium
Etc.
Occurence in UGA
Euplotes
Multiple codons must decode the same amino acid
Degenerate
Once the reading is commenced at a specific codon, the message is read in a continuing sequence of nucleotide triplets until a stop codon is reached.
No punctuation
For a given codon in the mRNA, only a ____ species of tRNA molecule possesses the proper anticodon
Single
In general, the third nucleotide in a codon is less important than the ____ in determining the specific amino acid to be incorporated
First two
First codon of an ORF present at the 5’ end
Start codon
Entry and exit channel for mRNA
Ribosome
an endergonic process that occurs at the expense of ATP, which loses two phosphate groups, becoming AMP
Linkage
base pair complementary to mRNA codons
Anti-codon loop
5’-CC—3’ which is the binding site of amino acids
Acceptor stem
Consists of anti-codon loop and acceptor stem
Transfer RNA (tRNA)
tRNA contains unusual and modified bases such as (5)
Uridine
Thymine
Pseudouridine
Methyguanine
Hypoxanthine
Etc.
