protein synthesis Flashcards
what affects the number of RNA polymerases binding DNA
transcription factors
how are transcription factors classified
according to structure of DNA binding domains
-zinc finger proteins
-helix turn helix proteins
-helix loop helix proteins
-steroid receptors
microbial drug targets in DNA and RNA metabolism, antibiotic and antiviral drug function
inhibits DNA metabolism of virus but not host
cancer drug targets in DNA metabolism
what causes mutations
what causes dna damage and how to reduce it
anticancer drugs target DNA synthesis, mutations caused by DNA are most common, free oxygen radicals cause DNA damage, reduce free radical levels by antioxidants
what happens in RNA processing
addition of 5’ (methyl guanosine) cap, protects mRNA from degradation and helps transcript bind to ribosome during protein synthesis
and splicing of introns
what does the addition of a 5’ cap do
protect mRNA from degradation and helps transcripts bind to ribosome during protein synthesis
alternative splicing in eukaryotes vs prokaryotes
eukaryotic genes are monocistronic, variants of protein encoded can be produced by alternative splicing
prokaryotic genes are polycistronic, one mRNA can code different proteins
what is alternative splicing
genes can form multiple proteins by joining different exon segments in primary transcript
what is the regulation of translation and mRNA decay mediated by
untranslated regions of mRNA
what does mRNA do
contains code, transcribed from DNA, introns and exons
what does tRNA do
carry specific amino acids to corresponding codons in the mRNA using its anti codon, clover shape
what is rRNA
site that links amino acids, forms a ribosome
what protein factors are required for peptide synthesis
initiation, elongation, termination
describe the codon
degenerate- more than 1 codon can code for the same amino acid
universal- codes for the same amino acids in all creatures
specific- particular codon always codes for the same amino acid
non overlapping- code read from a fixed start
describe the 3 main steps of protein synthesis
initiation- finds start codon of mRNA and puts first tRNA in P site
elongation- transfer of peptide chain to a new tRNA and moving this new tRNa into P site and putting next codon in the A site
termination- recognition of stop codon in A site, chain dissociates from tRNA, mRNA released from ribosome
what is P and A site and E site
P= peptidyl tRNA site, peptidyl tRNA placed before peptide bond formation
A= acceptor tRNA site, aminoacyl tRNA recognises codon
E= uncharged tRNA exiting the ribosome is localised
differences in protein synthesis in eukaryotes and prokaryotes
-prokaryotic mRNA is polycistronic and eukaryotic mRNA is monocistronic
-start codon is formyl methionine in prokaryotes and amino acid methionine in eukaryotes
-initiation in eukaryotes requires at least 10 initiation factors, 3 in prokaryotes
-prokaryotic ribosome is major target for antibiotics
what is polycistronic and monocistronic
monocistronic- encodes for a single protein
polycistronic- single mRNA can encode several proteins
how is the mRNA codon read
5’ to 3’
which is the leading strand in DNA
3’ to 5’
how is DNA read
3’ to 5’
describe the elongation step
-addition of amino acids to carboxyl end
-5’ to 3’ of mRNA
-entry of A site facilitated by elongation factors
-peptidyl transferase catalyses peptide bond formation
what catalyses peptide bond formation in elongation
peptidyl transferase
post translational modifications and explain them
glycosylation- addition of specific sugar molecule to protein in ER of golgi, makes glycoproteins
lipidation- anchoring membrane proteins
phosphorylation- switching on/off enzymes and receptors
hydroxylation of lysine and proline- stabilising structure of collagen
what are siRNAs and what are they used for
synthetic perfectly base pairing microRNA, used to reduce expression of a particular gene
what are used for biomarkers
microRNAs
codons of mRNA
AUCG
how do mutations form
alterations in nucleotide sequence
energy sources for mRNA translation
ATP and GTP
