Control Of Gene Expression Flashcards
(245 cards)
Do all cells contain the same genes?
Yes but different genes are expressed in each cell type
What is a gene from the perspective of a molecular biologist
A sequence of genomic DNA that encoded a single functional RNA
Give the 4 key steps in protein synthesis from DNA
Which steps are regulatory
Transcription-> splicing -> editing and export-> protein synthesis and degradation
All of them
Is protein synthesis from DNA compartmentalised
Yes
Transcription is in the nucleus and translation is in the cytoplasm
What are Exon’s and introns
What are promoters
Exon: expressed DNA segments
Introns: intervening sequences
Promoter: sequences which ensure that the gene is transcribed at the appropriate time and in the correct cell type
In mRNA what are coding regions flanked by
Untranslated regions (UTRs) at both 5’ and 3’ ends
Which RNAs are most abundant
tRNA and rRNA
How often do prokaryotic cells divide
Every 20 mins
How is prokaryotic DNA adapted for speed and rapid response to altered environment
No nucleus
No introns
mRNA is translated while still being transcribed
What is antitermination
The prokaryotic cell’s aid to fix premature termination of RNA synthesis during RNA transcription and often occurs when RNA polymerase ignores the termination signal and continues until a second signal is reached
What is transcription
What is it catalysed by
In what direction does it occur
The synthesis of single stranded RNA from a double stranded DNA template
Catalysed by RNA polymerase
Occurs in 5’ to 3’ direction
For any region of dsDNA what is copied by RNA in prokaryotes
Only one strand (the coding strand)
Is transcription continuous?
No it occurs in discrete units
Compare the length of the completed RNA chains to the whole bacterial DNA
What does this suggest?
RNA: 100 - 10,000 nucleotides
DNA: 4.7x10^6 nucleotides
RBA is copies in discrete units in the continuous DNA molecule with well defined starting and stopping points
Which strand on dsDNA may act as the coding strand
Either can
In bacterial, how many RNA polymerases are required
Only one RNA polymerase synthesises all mRNA, rRNA, and tRNA
How long do rRNA and tRNA molecules in bacterial cells last
They are very stable and persist for many generations
Compare the stability of rRNA, tRNA, and mRNA
rRNA and tRNA persist for many cell divisions due to their high stability
mRNA is rapidly degraded and replaced
The average half-life of E. coli mRNA is 2 minutes
What is required for prokaryotic RNA synthesis
DNA template to copy
riboNTPs (eg ATP, GTP)
No primer needed
What riboNTPs are required for prokaryotic RNA synthesis
APT
GTP
CTP
UTP
How does the precursor NTP interact with a growing RNA chain
What is the NTP usually
The phosphate attached to the 5’-OH terminus of the precursor NTP forms an Ester bond with the 3’-OH at the end of the growing chain with concomitant release of phosphate
ATP or GTP
What is on the very 5’end of an RNA chain
A triphosphate
How does the newly created RNA strand relate to the 2 strands of DNA
It is complementary and anti parallel to the template strand
It has the same sequence (replacing U with T) as the coding strand
What is the error frequency in prokaryotic RNA production
1 error per 10^4 nucleotides