Transcription & Translation Flashcards
What happens during initiation in transcription?
Code is recognised - transcription factors bind at TATA region (upstream of gene) and attract RNA polymerase (transcription initiation complex)
What happens during elongation in transcription?
RNA polymerase travels along templates strand and carries out complementary base pairing to form mRNA. 5’ to 3’ growth
What happens during termination in transcription?
Sequence-dependent termination of RNA chain growth. Methyl-guanine cap to the 5’ end which is then bonded with a 5’-5’ triphosphate link for stabilisation. 3’ end is polyadenylated (tailing)
What is splicing?
When the introns and exons are removed from the pre-mRNA
Describe mRNA
RNA polymerase II, 100,000s of kinds, a few copies of each present
Describe rRNA
RNA polymerase I, few kinds, many copies of each
Describe tRNA
RNA polymerase III, ~100 kinds, very many copies of each
What is the role of rRNA?
Used to bind to the mRNA and provides location for tRNA. Eukaryotes - 80S - 60S & 40S sub-units, prokaryotes - 70S - 50S & 30S sub-units
What is a charged tRNA molecule referred to as?
Aminoacyl-tRNA
What is the wobble position?
Aspecific region in a tRNA molecule
What is the function of transcription factors?
GIves transcription a direction
What happens in donor site is mutate?
Splicing site is inhibited which can cause diseases
What post-translational processes occur to transform pre-mRNA into mature mRNA?
Capping, tailing and splicing
What happens during initiation in translation?
At 5’ cap end - 40S subunit binds to Met-tRNA (AUG recognition). 60S subunit then binds allowing elongation to occur
What happens during elongation in translation?
N - C chain growth. Met-tRNA occupies P site, another aminoacyl-tRNA occupies A site (requires GTP). Methionine forms a peptide bond with next aa causing tRNA in P site to become uncharged. Translocation. Enzyme - peptidyl transferase
What happens during termination in translation?
Stop codon (UAA, UAG or UGA - no corresponding tRNAs). Hydrolysis occurs to release the proteins into the cytoplasm
Describe the structure of a tRNA molecule
Clover model, single stranded, uncharged. Amino acids activate them
What is the function of the P site?
Holds the peptide chain
What is the function of the A site?
Site accepting the tRNA
Describe a bacterial cell’s components in regards to transcription and translation
Simpler promoters, different transcription factors, single RNA polymerase, coupled transcription-translation, no post-transcriptional processing, short-live mRNAs, simpler ribosomes (attack only 30S), distinctive translation initiation mechanism, different translation factors.
How can mutations outside the coding region affect gene expression?
Promoter region mutations can affect gene expression - either activate or deactivate it.
