RNA transcription and regulation Flashcards
From DNA upwards, how is DNA folded and packed? (3)
DNA winds into chromosomes, from there into nucleosomes, and finally into solenoids
What is the large, general difference between euk and prok in regards to DNA being transcribed into DNA?
Prok transcribes directly into mRNA
Eukaryotes transcribe into pre mRNA first, then mature it into mRNA
Why does DNA and RNA always transcribe in the 5’-3’ direction?
The phophodiester bond can only occur at the 3’ end of the nucleotide already on the strand
How does the transcription signaling protein hold onto the DNA strand and find the correct sequence?
non specific affinity to the dna strand, random match affinity, and then finally it attaches to the correct sequence when that affinity matches its own affinity exactly
what polymerase is used in prokaryotes for transcription?
RNA polymerase
What polymerase is used in the eukaryotes?
RNA polymerase II
How is transcription triggered in prokaryotes?
little subunits find specific regions on the DNA and attact RNA polymerase which transcribes the mRNA
How is transcription triggered in the Eukaryotes?
a group of activators, repressors, and transcription factors assemble at the regulatory sequence, which attracts RNA polymerase II to bind and transcribe
what is the group of repressors, transcription factors, and activators called?
Transcription Initiation Complex (TIC)
give three examples of transcription factors described in class
steroids, MAP kinase, and PKA
How are RNA polymerase I and III different from II?
They can only assist in producing protein, by providing ribosomes (I) and bringing amino acids (III)
describe the distal regulatory sequence
activators, represors, and transcription factors can bind to it upstream by hundreds of nucleotides, and regulate the transcription of the sequence
What region of the strand contains the TATA box?
The promoter
what two processes are used to stop transcription in proks?
Rho independent and dependent
At what rate can RNA polymerase II transcribe?
60 nucleotides per second
describe Rho independent in prokaryotes
The independent process has lots of G and C at one end that attract to eachother and make a loop. the tension this loop makes at the end causes the TIC to fall off the strand
Describe RHO dependent in prokaryotes
An ATP powered unwinding enzyme causes the TIC to fall apart
What is used by eukaryotes to halt transcription?
a sequence of DNA at the end of the sequence
How does the Eukaryote use the sequence of DNA at the end of the sequence to halt transcription.
The sequence signals the polymerase to stop soon, and that sequence itself is translated. The polymerase stops transcribing shortly therafter. But that leaves an extra segment that is not part of the desired sequence
What is the extra segment of DNA used for after transcription has halted in eukaryotes?
It is used to attach the Poly-A tail. The Poly-A tail attaches to it.
What enzyme is used to attach the Poly-A tail?
Poly-A polymerase
how do the products of transcription differ between eukaryotes and prokaryotes?
straight up mRNA will come from prokaryotes, while pre mRNA will come from eukaryotes first
what things must happen to pre mRNA before it can become mature?
it must have the 5’ G cap added, and the poly A tail added to the 3’ end, and the introns spliced out
do both euk and prok have introns?
No, only eukaryotes have introns
where is the poly A tail added to?
It is added to a small amount of extra dna that is at the 3’ end
when is the 5’ cap added to the mRNA strand?
shortly after translation initiates, roughly 50 nucleotides in
what is the role of the 5’ cap?
It attracts the ribosme 30S to the strand
what is the mechanism used for the splicing of the introns?
snRNPs (small nuclear ribonuclear proteins)
what are snRNPs made of?
short nuclear RNA and proteins
How does the spliceosome know where to cut the mRNA?
the complex that is formed is able to recognize the specific sequences of RNA
How can these spliceosomes create different sequences from the same mRNA strand?
The spliceosome can recognize sequences on either end of introns that have a exon in between them. This can create different proteins by expressing the exons differently
How can these spliceosomes create different sequences from the same mRNA strand?
The spliceosome can recognize sequences on either end of introns that have a exon in between them. This can create different proteins by expressing the exons differently
how is gene expression regulated in prok?
Operons, molecular switches
how many proteins are needed to digest lactose?
3
In prokaryotes, what lies between the promoter and the sequence it corresponds to?
operator
what role does a repressor play in gene expression in prok?
The repressor binds to the promoter, which prevents RNA polymerase from binding
where is the sequence that codes for the repressor?
upstream
what can allow the repressor to drop of the promoter?
when lactose becomes available in higher concentrations, a modified version of lactose will bind to the receptor and make it drop off
what is the modified version of lactose called that binds to the repressor?
allactose
what converts lactose to allactose?
beta galactosidase
what enzyme makes lactose permeable to the cell?
permease
what is interfering RNA?
small strand of RNA that can bind to specific sequences of mRNA, and tag them for degradation
what is interfering RNA?
small strand of RNA that can bind to specific sequences of mRNA, and tag them for degradation
From DNA upwards, how is DNA folded and packed? (3)
DNA winds into chromosomes, from there into nucleosomes, and finally into solenoids
From DNA upwards, how is DNA folded and packed? (3)
DNA winds into chromosomes, from there into nucleosomes, and finally into solenoids
what are transposons?
segments of DNA that are able to be excised and transplanted in a different region of the strand
who discovered transposons?
Barbara McClintock
what enzyme is responsible for cutting out the jumping genes?and inserting them in a different section?
transposase
what enzyme is responsible for cutting out the jumping genes?and inserting them in a different section?
transposase
define retrotransposons
segments of RNA that can code for DNA via reverse transcriptase, then be placed into a gene
what is really bad about transposons?
They have no proofreading system, so they make a lot of mutations
what are ribosomes made of?
ribonucleoprotein
