pack Flashcards
(17 cards)
What mutation causes sickle cell anemia?
Point mutation in b-hemoglobin which turns glutamate into valine (missense)
What causes huntington disease?
amplification of the CAG codon which causes extra glutamine
What type of mutation causes cystic fibrosis?
Mutation in the CFTR which prevents chloride transport causing mucus to build up.
What is the mutation in the CFTR called?
ΔF508 in which the codon TTT is deleted causing Phe to not be coded
What are the 4 start and stop codons?
Start: AUG
Stop: UAA UGA UAG
What is the nonsense mutation?
Point putation in a codon that results in it turning into a termination codon.
(stop talking nonsense)
What is the missense mutation?
Point mutation turns a codon into another codon
(misunderstanding)
How is the mRNA codon read?
The mRNA codon is “read” 5’→3’ by an anticodon pairing in the “flipped” (3’→5’) orientation.
What do small and large ribosomal subunits do?
The small ribosomal subunit binds mRNA and is responsible for the accuracy of translation by ensuring correct base-pairing between the codon in the mRNA and the anticodon of the tRNA.
The large ribosomal subunit catalyses formation of the peptide bonds that link amino acid residues in a protein.
What are the EPA sites?
(Sites between small and large ribosomal subunits)
The A site is the point of entry for the aminoacyl tRNA (except for the first aminoacyl tRNA, which enters at the P site). The P site is where the peptidyl tRNA is formed in the ribosome. And the E site which is the exit site of the now uncharged tRNA after it gives its amino acid to the growing peptide chain.
What happens in elongation?
During elongation, the ribosome moves from the 5’ -end to the 3’-end of the mRNA that is being translated.
The formation of the peptide bond is catalysed by peptidyltransferase, an activity intrinsic to the 23S rRNA found in the large (50S) ribosomal subunit.
Because this rRNA catalyses the reaction, it is referred to as a ribozyme.
After the peptide bond has been formed, what was attached to the tRNA at the P site is now linked to the amino acid on the tRNA at the A site.
When does termination occur? What recognizes it?
Termination occurs when one of the three termination codons moves into the A site of the 60S subunit.
These codons are recognized by release factors.
What is translocation?
The ribosome then advances three nucleotides toward the 3’-end of the mRNA. This process is known as translocation.
(The ribosome moving three nucleotides away to make space for three new nucleotides.)
What happens in translocation in regarding to the EPA sites?
Translocation causes movement of the uncharged tRNA from the P to the E site (before being released), and movement of the peptidyl -tRNA from the A to the P site.
What is a polyribosome?
A polyribosome is a complex of multiple ribosomes that work on translating a single mRNA all at once.
What are endoproteases?
They cleave parts of a precursor protein
(like amyloid precursor protein)
What are zymogems?
Zymogens are inactive precursors of secreted enzymes
