Translation Flashcards
Translation
process of translating the language of nucleotides into the language of amino acids
Where does translation occur?
ribosome via. instructions provided by mRNA
mRNA is translated in what direction?
5’ to 3’
mRNA is translated into
proteins
start codon for translation
AUG (methionine)
Codon
genetic code is read in groups of 3 nucleotides
The degenerate nature of the genetic code
more than one codon can code for the same amino acid
Unambiguous nature of genetic code
each codon only specifies one amino acid
wobble
third base deviates from the base pairing rules or is an unusual base
mutations
arise as a result of DNA damage or incorrect incorporation of bases
point mutation (substitution)
a single base changes (CGA –> CGG)
silent mutation
a change that specifies the same amino acid (CGA –> CGG)
missense mutation
a change that specifies a different amino acid (CGA –> CCA)
nonsense mutation
A change that produces a stop codon (CGA –> UGA)
insertion mutation
an addition of one or more bases (CGAG –> CFATG)
deletion mutation
A loss of one or more bases (CGAG –> CGG)
frameshift mutation
mutation that shifts the reading frame of the genetic message by inserting or deleting a nucleotide
proceeding of translation
- charged tRNAs donate their aa to the growing chain while the anticodon is attached to the mRNA
- tRNA is released and charged tRNA codes for the next aa in the reading frame becomes attached
3 steps of translation
initiation, elongation, termination
initiation
formation of a complex between the methionyl-tRNA, initiation factors, the mRNA, and thee smallest ribosomal subunit (40S), 60S subunit binds to complete
binding sites on ribosome
A (aminoacyl), P (peptidyl),
Elongation
peptidyltransderase, the rRNA of the large ribosomal subunit catalyzes the formation of the peptide bond
termination
- stop codon reached (UGA, UAG, UAA)
- release factors bind to ribosome, allowing last peptide bond to form before ribosome falls apart and releases protein
- requires lots of energy
posttranslational modification
removal of N-terminal methionine, cleavage
polysomes
multiple ribosome can attach to an mRNA, each producing the same protein
signal sequence
sequence within a protein that directs the protein to a particular organelle
Signal-reecognition particle (SRP)
- secreted or incorporated membrane proteins are translated in the ER due to SRP
- cause the ribosome to dock onto the ER to complete synthesis of the protein
proteins synthesized into the ER
travel in vesicle to Golgi complex, but do not remain, become lysosomes or fuse within the cell membrane
