molecular biology 3 Flashcards
what are 3 differences in the structures between RNA and DNA
- RNA does not consistently fold in a base paired manner
- RNA contains a lot of pseudo knots and complex structures
- RNA structure is a lot less stable than DNA secondary structure
5 functions of RNA
- genetic messenger
- guide RNA’s like telomerase
- adaptor RNA
- structural RNA
- catalyst
what unwinds dna for transcription
RNA polymerase II
what is the template for RNA
dna
describe the transcription of RNA
- uses RNA polymerase from 5 - 3
- not as accurate as dna replication
what are the 2 strands called in dna- rna transcription
template strand and coding strand
what is the difference in the number of copies made for DNA and RNA transcription
DNA = just one
RNA = multiple chains will be developed because multiple RNA polymerase work together at the same time.
what do promoters contain
specific DNA sequences that provide a secure initial binding site.
what is the promoter region called for RNA polymerase II
TATA region
but TBP will distort DNA once bound (this is a transcription factor)
what are transcription factors
they are proteins that regulate gene transcription
what are the 3 types of RNA polymerase
RNA polymerase I- rRNA
RNA polymerase II - protein coding RNA
RNA polymerase III - tRNA
what does the TATA region do and where will you find it
it facilitates RNA polymerase and transcription factors and you will find it in the minor groove
what are house keeping genes
they are genes that are required for the basic cellular maintenance function
what does the promoter region do
it is a sequence that tells RNA polymerase to start transcribing at a set position, it can recruit accessory proteins.
what do enhancers do
- increase likelihood transcription will occur
- stables the transcription machinery
- they ensure conditions are right for RNA polymerase to initiate transcription
what are the 2 domains of transcription factors
DNA binding domain
activation domain = facilitates other protein to protein interactions
what does RNA polymerase require to become active
accessory proteins
how does RNA polymerase know to stop transcribing
because there are also bases in the terminator area which tells RNA polymerase to stop transcribing and fall off
what are enhancer opposed by
silencers
what are the 2 ways chromatin is modified to allow RNA polymerase access?
- Histone modified enzyme
- chromatin remodelling complex remodels nucleosomes
what are the 2 types of responses to extra cellular signalling molecules?
1- when the protein machinery is already there and it only has to be altered, it will take seconds
2- when the protein has to be made, translation and transcription, can take mins/hrs
what are 6 different ways transcription can be activated?
- protein synthesised
- protein phosphorylated
- protein dephosphorylated
- ligand binding
- release from an inhibitor
- change of binding partner
aniridia
this is when there is no iris in the eye caused by the lack of transcription factor PAX6
what are 2 modifications of pre-messenger RNA
RNA capping = methyl G capping (RNA transcription normally starts with a G at 5’ end- this is what allows the mRNA through the nuclear pore)
polyadenylation = at the end of the pre messenger RNA 3’ end, polyadenylation is added which is a chin of repeating A bases
what are 3 reasons for pre messenger RNA modifications?
- protect from exonuclease
- aids export into cytoplasm from nucleus for translation to occur
- to identify the strand as mRNA
explain splicing
introns need to be removed in order to produce a mature mRNA which has an open reading frame that only contains exons.
the mature mRNA will then move to the cytoplasm fro translation
difference between introns and exons
introns= regions that do not encode protein
exons = regions of DNA that do code for proteins
what are responsible for splicing and how does it take place
- spliceosomes are responsible for RNA splicing
- these proteins carry snRNA which recognise the specific sequences at the intron-exon junction.
what type of reaction is splicing
esterification
what are the 2 steps in splicing
1- branch site attacks intron-exon junction which forms a free hydroxide group at the 3’end of the Xon and a lariat structure.
2- the hydroxide group then attacks another intron-exon junction in order to release the lariat junction which leaves the exon mRNA
how are exons recognised in pre-mRNA
the sn-RNA region of the splicisome looks for the sequence in the intron exon junction and form a base pair with these sequences
what can alternative RNA splicing do
it can cause exon skipping which means an exon is left out of the mature mRNA after splicing
resulting in the production of different mRNA transcripts that will make proteins with different functions.
what is Frasier syndrome
a kidney disease that causes FSGS which where scar tissue forms in the kidney glomeruli.
what is Frasier syndrome caused by
caused by a mutation in a tumour suppressor gene
different amount of +KTS (less of this) and -KTS which stems from exon 9
what are 5 ways that different proteins can be made from the same gene
- alternative promoters
- alternative splicing
- alternative 3’ ends
- RNA editing
- translational control
