GENE EXPRESSION RECAP Flashcards
Function of rRNA
form core of ribosome and catalyse protein synthesis
central dogma
DNA –> RNA –> Protein
RNA produced is complementary to __(a)__ and identical to __(b)__
a) template
b) coding
Where does PROKARYOTIC TRANSCRIPTION initiate?
- begins at gene promoter which is a region of DNA upstream of a gene
What are the roles of sigma factors in initiating transcription? How is this different in eukaryotes?
serve to bind elements of DNA promoters to create DNA polymerase complex
- transcription factors used in eukaryotes to recruit DNA polymerase
How is transcription terminated?
intrinsic termination after inverted repeats to form an RNA stem loop
RNA polymerase does not require DNA _____
helicase
Function of amino-acyl tRNA synthetase
ensures that the the tRNA molecules are charged with the correct amino acids
3 translation steps
Initation
Elongation
Termination
In prokaryotes, 30S ribosomal complex is recruited to the ___ binding ____.
a) ribosome
b) site
Function of initiation factors in translation
helps formyl-Met/initiator tRNA bind to the start codon allowing 50S unit to approach
Difference between eukaryotic and prokaryotic ribosomes
eukaryotes have their subunits precharged with Met-tRNA
Describe translation
1) initiation codon, usually AUG, positions the reading frame of mRNA
2) translation proceeds from initiation to first stop codon (open reading frame)
3) codons bound to aminoacy tRNA
- each codon linked together by peptide bond at ribosome acceptor A and by a peptidyl transferase
4) peptide chain formed
What is an open reading frame?
First start codon to first stop codon
How is translation terminated?
release factors which recognise STOP codon release the peptide and ribosome recycling factor causes disassociation of ribosome
Majority of eukaryotic genome is ___
introns, non-coding
What is a transcription unit in eukaryotes?
The equivalent in prokaryotes?
- has promoter upstream of the 5’ end to recruit RNA pol
- operon
Function of transcription factors
to recruit RNA pol
What are enhancer sequences?
places that TF’s bind to influence and therefore increase the rate of transcription initiation
TATA box is an example of a
promoter region
Functional RNA genes are not ______.
Instead?
translated
- they are synthesisesd in the nucleus
rRNA is synthesised using RNA pol (a) in the __(b)__
a) 1 b) nucleolus
tRNA is synthesised using RNA pol _(a)__ in the __(b)___
a) III b) nucleus
mRNA is synthesised using RNA pol __(a)___ in the __(b)__
a) II b) nucleus
What is the use for the 5’ cap?
ribosome binding
Coding exons must be (a) together before translation. . This occurs in a large complex called the __(b)___ and introns form a __(c)___ structure during removal. ___(d)____ splicing means that one gene can make a variety of __(e)___ products.
a) spliced
b) splicosome
c) lariat
d) alternative
e) protein
a) What is a poly-adenylated tail?
b) What is its function?
c) How is it formed?
a) sequence of repeated A bases
b) to protect against degradation and to influence translation
c) AATAAA poly A signal causes the primary transcript to have around 20 bases cleaved downstream of the poly A signal and poly A tail synthesised from that point
a) What is muscular dystrophy?
b) distinguish between Duchenne and Becker MD?
a) defects in dystrophin gene Xp21 exons
b) DUCHENNE - no functional protein produced due to deleted exon
BECKER - reading frame maintained giving a semi functioning protein
