lecture 14 Flashcards
what is at the beginning of every protein sequence?
AUG
- methionine is at the beginning of every amino acid sequence but does not need to be there when it is matured
Translation is
the synthesis of protein from mRNA
Translation
-what and where?
takes info from nucleic acids (ribonucleotides) and translates it into proteins (amino acids)
takes place in the cytosol
Genetic code is
a set of triplet code codons in mRNA or DNA that codes form amino acids
genetic code— what dictates the amino acid?
the first two bases
*makes sense if we look at the table
open reading frame (ORF) definition
a reading frame that has the potential to code for a protein or peptide
ORF details
the first base of the ORF is a start codon
ends with a stop codon
usually more than 50 codons
4 types of mutations
missense
nonsense
silent
frameshift
missense mutation
a single nuc change results in a codon that codes for a diff amino acid
nonsense mutation
point mutation that results in a premature stop codon
silent mutation
takes place in nonessential part of a gene. no effect on the gene product
tRNA function
acts as a bridge between RNA and protein
aminoacyl-tRNA synthesases
couples the correct amino acid to the correct tRNA molecule using ATP
–> when coupled, the tRNA is “charged”
ribosomes function in translation
translation is conducted by ribosomes in the cytoplasm
ribosomes are large complexes of
rRNA (2/3) and protein (1/3)
ribozymes are
RNA molecules w catabolic activity
what dictates the structure of the ribozyme?
rRNA in ribosomes
rRNA allows for the catabolic activity of ribosomes
3 sites on the ribosome
A= aminoacyl-tRNA site
P= peptidyl-tRNA site
E= exit site
what is the difference between translation in bacteria compared to eukaryotes?
v similar but in bacteria:
-mRNA has no 5’ cap so the small subunit recognizes the “Shine-Dalgarno” sequence instead
-bacteria has polysictronic mRNA
-each individual gene will have a shine-dalgarno sequence so each product is translated independently
polycistronic mRNA
several genes encoded on the same mRNA transcript
(bacteria has this)
monocistronic mRNA
eukaryotes have this
one gene encoded on the mRNA transcript?
polyribosomes
how are they made?
a single mRNA transcript can be translated by several ribosomes at the same time to form a polyribosome
polyribosomes
-increases what?
-occurs in?
increases overall rate of protein synthesis
occurs in both euk and prok
proteases
enzymes that degrade proteins
proteosomes
a large protein machine that degrades proteins in euk
unfolds proteins and degrades them
autocatalysis
the ability to catalyze rxns that lead to production of molecules like itself
- RNA molecules can catalyze their own synthesis
