Translation

How does protein synthesis fit into the Central Dogma of Molecular Biology?


  • It states genes flow from DNA to RNA to protein and synthesis helps translation so that flow can happen.


RNA plays a central role in protein synthesis. Explain.


  • It carries out all of the genetic instructions from the DNA to the ribosomes.


What are the five main players in protein synthesis and what role does each play in the process?


  • DNA: is the blueprint, and stores the genetic information, mRNA: is the messenger that carries the information to the ribosomes, tRNA: transfers the information to specific codons and amino acids, rRNA: is ribosomal RNA that structures the ribosome and creates the complex, Ribosomes: where protein synthesis happens


What are the special features of the genetic code that relate to protein synthesis?


  • The triple codons. This is the nucleotide language and takes three of the nucleotides and names it into a single amino acid. 




Why is the genetic code “almost” universal?


  • Almost all living organisms use these codons and this type of language but some species differ in the stop codons.


What advantages are there to having multiple codons for individual amino acids?


  • It acts as a buffer to help prevent mutation by having there be multiple ways of coding the same amino acid.


What is the effect on the final polypeptide of shifting the “reading frame” for DNA transcription?


  • This is a frameshift mutation and completely changes how the DNA is read changing the mRNA and leading to different amino acids being created. 


How do mRNA molecules in prokaryotes and eukaryotes differ?


  • Pork is polycistronic meaning it can get multiple proteins from mRNA while euk is monocistronic meaning it can only get one protein at a time.


In what direction is an mRNA read, where does it start, where does it stop, and exactly what is translated?


  • It is read from the 5’ end to the 3’ end and it starts at AUG and stops at one of the stop codons. Amino acids are being translated to form proteins.


How are monocistronic and polycistronic mRNAs distinguished?


  • By the number of proteins they can create and by the ribosome binding site. There is also no cap and no tail.


What is the advantage of polycistronic mRNA to an actively growing bacterium?


  • It can produce rapidly while expressing multiple proteins and it uses less energy to get more or something. 


What are the main structural features of tRNA?



  • The cloverleaf shape. It has three loops and an amino acid attachment site with an ester bond and an anti-codon loop


Where does the CCA on the 3’ end of a tRNA come from and what is its purpose?



How do “unusual” bases in the tRNA molecule arise, and why might they be important?



What is the most variable portion of a tRNA molecule?



How do codons and anticodons interact? How are they arranged concerning the inherent directionality of tRNA and mRNA?



What is the “wobble” hypothesis and what is its significance?



Can a given tRNA carry more than one type of amino acid?



Can different tRNAs accept the same amino acid?



What are the main distinguishing features of different tRNA molecules?



Can a given tRNA molecule recognize more than one mRNA codon? Why?



How do tRNA molecules get attached to the “correct” amino acid?



What is meant by a charged tRNA? An activated amino acid?



What distinguishes the ester bond that connects an amino acid to a tRNA?



How does the enzyme aminoacyl-tRNA synthetase “choose” the correct amino acid

for attachment to a given tRNA?



How important is the proper functioning of aminoacyl-tRNA synthetase to

cell function?



What protein and RNA components make up a fully functional ribosome?



In what capacity are the RNA components of ribosomes thought to function? When are functional (complete) ribosomes found in cells?



In which direction is an mRNA molecule “read“ by a ribosome? Which end of the polypeptide is produced first?



What are the major steps in protein synthesis?



What is the sequence of events leading to the initiation of prokaryotic protein synthesis? What accessory proteins are involved and what are their functions? What interactions occur between mRNA and the small ribosomal subunit? What part of the small subunit is involved in this interaction?



What is the “Shine-Dalgarno” sequence?



What is the A site, the P site, and the E site in a functional ribosome?



What are the major steps in the elongation phase of protein synthesis? How do accessory proteins contribute to the process?



What drives tRNA binding to the ribosome? What determines which tRNA will bind? Where does it initially bind?



What drives peptide bond formation? What drives translocation?



What are the main steps to the termination of prokaryotic protein synthesis?



How does a release factor serve to terminate protein synthesis?



What is a polyribosome and why is it an advantage to a cell?



What are the main differences between protein synthesis in prokaryotes and eukaryotes?



Can polyribosomes form in eukaryotic cells? If so, what might be the advantages of this method of translation?