Transcription + Translation Flashcards
Where is the TATA box located and how many BP away?
25-35 BP upstream
How common is the TATA box in cells
only present in 24% of genes
Which direction does transcription occur?
5’ to the 3’ direction
What molecules do RNA polymerase attach?
ribonucleoside triphosphate
What does DNA polymerase requires to take effect
Requires a primer as it needs an O-H group to bond to
error rate in transcription?
1 in 100,000
what does polycystronic mean
one strand of mRNA can code for multiple proteins
which end does the poly a tail attach to?
3’ end
how does the 5’ cap attach?
7-methyl guanosine triphosphate attaches via a 5’ to 5’ triphosphate link
What amino acid starts translation?
AUG - methionine
What is the starting amino acid in bacteria and why is this good?
N-formylmethionine - allows immune system to identify foreign bacterial cells
what is the site order in translation?
A site then P site then E site
What are the three stop codons
UGA UAA UAG
which site do release factor bind to?
A site
What is wobble and where does it occur
occurs at 1st base on anticodon, 3rd base of codon (mismatch of amino acids
what are the 3 types of rna
mRNA - carries RNA to ribosomes for translation - make up 5% or rna
rRNA - ribosomal rna (most common) combines with other enzymes and proteins for protein synthesis
tRNA - smallest amount - transfer amino acids during protein synthesis
what are the differences between DNA and RNA
RNA: has a uracil not a thymine
is ribose sugar and - deoxyribose lacks a hydroxyl on the second group
what are the 3 RNA polymerases and what do they do
Polymerase 1 - transcribes ribosomal RNA
Poly 3 - transcribed tRNA
poly 2 - transcribes mRNA, microRNA and non-coding RNAs
what is tata box
promoter element composed of T’s and A’s
what happens in splicing
removal of introns (non-coding sequences)
what happens in polyadenylation
addition of many A’s at the 3’ end which reduces chance of enzymatic degradation and helps with identification and termination of transcription
what is a 5’ cap
7 - methylguanosine ppp added to 5’ end which stabilising the mRNA
what is CpG island and why are they relevant
stretches of DNA where C is followed by G - appear t have an effect on promotor regions. In x inactivation CpG island is methylated which stops expression of a gene
how are introns removed
by a spliceosomewhich produces a lariat loop with an OH at the 3’ end
describes the steps in mRNA packaging
RER with ribosomes to Golgi (cis - trans) secretion into the plasma membrane
what is a disulphide bridge
bond between two cysteine residues
describe the process of insulin production
preproinsulin - signal sequence is cleaved off in the pancreas in B cells
proinsulin - disulphide bonds form in the ER
Insulin - the connecting C-peptide loop is cut away in secretory granules by proteases
which enzymes add amino acids on the 3’ end of newly synthesised tRNA molecules
aminoacyl - tRNA synthetases (tRNA ligase)
how is the correct amino acid added to polypeptide chain
anticodon is specific and there is proof reading glelemtn by the RNA synthetases
