Bio Lecture 17 Translation Flashcards
What is always the first amino acid in a protein?
Methionine
formyl-methionine in prokaryotes
What direction is the mRNA read for translation?
5’-3’
What direction are amino acids laid down for the formation of proteins?
N-C terminus
What are the stop codons?
UAA
UAG
UGA
What does it mean that the genetic code is degenerate?
It is redundant. Meaning there are several codons that code for the same amino acid. Only Methionine and Tryptophan don’t have multiple codons.
What are the 4 types of mutations?
Missense: base substitution causes change in amino acid
Nonsense: base substitution causes a premature stop
Silent: base substitution has no effect
Frameshift: insertion or deletion causes a change in the reading frame
What is the name for the RNA code in tRNA’s that matches with the codon? Where does the amino acid bind to the tRNA?
Anti-codon
Amino acids bind to the 3’ end of the tRNA
How do amino acids get attached to tRNA’s?
Aminoacyl-tRNA synthetases bind the two together using ATP. These synthetases are unique to each amino acid, and they are able to remove incorrect amino acids if needed.
What are the components of a ribosome?
Large subunit catalyzes the polypeptide bond
Small subunit does initiation, decoding, and binds to the mRNA and tRNA
What are the binding sites in ribosomes?
All the sites bind to tRNA in its three different forms
A: Aminoacyl-tRNA bind here and the polypeptide bond is formed at this site
P: Peptidyl-tRNA, carries the chain of amino acids already synthesized
E: Exit, holds the tRNA that no longer has an amino acid attached
What are the types of proteins used for translation in both prokaryotes and eukaryotes and how are the abbreviated?
Initiation factors (IF's) Elongation factors (EF's) Release factors (RF's)
When in eukaryotes, add an e before each such as eEF3.
What is the Shine-Dalgarno sequence?
In prokaryotes, and used for translation.
It is a sequence in the mRNA upstream from the start codon that tells the small ribosomal unit where to bind and start translation.
What does polycistronic and monocistronic mean?
Prokaryotes have mRNA that is polycistronic which means that the mRNA codes for multiple proteins. Eukaryotes are monocistronic, meaning each mRNA only codes for one protein.
Explain eukaryote translation initiation.
1) Charged initiator tRNA binds to eIF2 which is bound to GTP
2) The above then bind to the small ribosomal subunit so the tRNA is in the P site
3) At the same time, eIF4E&G bind the 5” cap of the mRNA
4) Small subunit binds to the 5’ end
5) Small subunit scans for first AUG to start
6) GTP is hydrolyzed and eIF2 leaves
7) Large subunit comes
What are the differences in translation elongation between prokaryotes and eukaryotes?
The elongation process is conserved between the two.
