Lecture 16 Flashcards
True or False: The genetic code of humans (which codon encodes each amino acid) is almost universal.
TRUE
What are the names of the three stages of translation?
Initiation, Elongation and Termination
What are the major molecules that take part in translation?
The major molecules are mRNA, tRNA, ribosomes and amino acids.
What is a ribosome and what type of molecules is it made up of?
A ribosome is a protein consist of two subunits; the small ribosomal subunit, which reads the RNA, and the large subunit, which joins amino acids to form a polypeptide chain. Each subunit is composed of one or more ribosomal RNA (rRNA) molecule and a variety of proteins.
What two molecules bind to the mRNA to initiate translation?
The small subunit of the ribosome and the aminoacylated tRNA both binds to the mRNA to initiate translation.
What attaches the amino acid to the tRNA? Is there one for each amino acid, or is there one that does all of them?
The aminoacyl-tRNA synthase is responsible for adding the correct amino acid to the correct tRNA. There is a least one tRNA for every amino acid.
What type of bond is there between the tRNA and amino acid?
The tRNA is covalently bounded to the amino acid.
What is the critical sequence in the tRNA that directs translation? What is the name of the sequence and why is it so important? How does it relate to the mRNA?
….Anti codon? It is complementary to the codon on the mRNA and coordinates the amino acid to the polypeptide being produced.
Why is a silent mutation?
A silent mutation is a point mutation in which a single nucleotide change results in a codon that codes for the same amino acid. It causes no change to the polypeptide being produced.
What is a missense mutation?
A missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It may cause the change in the function of the protein being produced depending on the importance of the changed amino acid.
What is a nonsense mutation?
A nonsense mutation a point mutation in the DNS sequence that results in a premature STOP codon. This may have an adverse effect on the protein produced.
What might a frameshift mutation cause?
A frameshift mutation can drastically change the protein being produce as it would change the length of the DNA sequence of that certain gene. Mutation may have come from during replication/transcription.
How does a prokaryotic ribosome identify the initiation codon in an mRNA?
mRNA in prokaryotes have a Shine-Dalgarno sequence before the START codon that allows the prokaryotic ribosome to identify the initiation codon.
What part of the eukaryotic mRNA is initially recognised and bound by the ribosome?
The ribosomes in eukaryotes bid to the 5’ cap and then finds the initiation codon with some help from a sequence called the Kozak consensus sequence (not as strong as the Shine-Dalgarno).
The three sites in the ribosome are E, P and A. What is each site named for?
The A site is where the aminoacyl tRNA binds. The P site is where the peptidyl tRNA The E site (exit site), the final transitory step before a tRNA now bereft of its amino acid is let go by the ribosome.
