Download Chapter 15 - Translation of mRNA

Chapter 15
Translation of mRNA
Study Outline
1. The genetic basis for protein synthesis
a. Archibald Garrod proposed that some genes code for the production of a single enzyme
b. Beadle and Tatum’s experiments with Neurospora led them to propose the one-gene/oneenzyme hypothesis
2. The relationship between the genetic code and protein synthesis
a. During translation, the genetic code within mRNA is used to make a polypeptide with a
specific amino acid sequence
b. Exceptions to the genetic code are known to occur, which includes the incorporation of
selenocysteine and pyrrolysine into polypeptides
c. A polypeptide chain has directionality from its amino-terminal to its carboxyl-terminal
end
d. The amino acid sequences of polypeptides determine the structure and function of
proteins
3. Experimental determination of the genetic code
a. Studies involving T4 phage indicated that the genetic code is read in triplets
b. Synthetic RNA helped to determine the genetic code
c. The use of RNA copolymers and the triplet-binding assay also helped to crack the genetic
code
4. Structure and function of tRNA
a. The function of a tRNA depends on the specificity between the amino acid it carries and
its anticodon
b. Common structural features are shared by all tRNAs
c. Aminoacyl-tRNA synthetases charge tRNAs by attaching the appropriate amino acid
d. Mismatches that follow the wobble rule can occur at the third position in codonanticodon pairing
5. Ribosome structure and assembly
a. Bacterial and eukaryotic ribosomes are assembled from rRNA and proteins
b. Components of ribosomal subunits form functional sites for translation
6. Stages of translation
a. The initiation state involves the binding of mRNA and the initiator tRNA to the
ribosomal subunits
b. Polypeptide synthesis occurs during the elongation stage
c. Termination occurs when a stop codon is reached in the mRNA
d. Bacterial translation can begin before transcription is completed
e. Bacterial and eukaryotic translation show similarities and differences