RNA and transcription W4 Flashcards
three main differences between RNA and DNA
RNA is single stranded
it contains Uracil instead of thymine
it contains ribose instead of deoxyribose
three main RNA species
messenger RNA (mRNA) ribosomal RNA (rRNA) transfer RNA (tRNA)
primary role of mRNA
directs amino acid sequence for proteins
primary role of tRNA
transports amino acids to site of protein synthesis
primary role of rRNA
part of ribosome, involved in protein synthesis
how is RNA made
via RNA polymerase
what directs the transcription process
DNA sequence
what is a promoter
start signal - TATA box: 5’TATAAA3’
what is the start signal recognised by
TATA protein (TBP)
what is the terminator
stop signal- 5’ AATAAA 3’ signals polymerase to stop
what controls the rate of transcription
transcription factors
what do transcription factors do
regulate the rate of transcription
how do transcription factors regulate the rate of transcription
by binding to specific DNA sequences in promter regions (DNA BINDING DOMAIN) and interract with proteins that are required for transcription to alter rate (ACTIVATION/REPRESSION DOMAIN)
what are the two types of transcription factors
general
specific
what is the difference between general and specific transcription factors
general - needed for transcription to occur, same ones required for all genes and cells
specific- not needed for transcription to occur, but they increase/decrease the rate`
specific transcription factors may be involved in …… or…..
activation or repression
specific transcription factors can be regulated by (3)
- cell specific expression
- translocation
- modification or binding interactions with other proteins
example of specific transcription factor
steroid hormone receptor -
only prompters with steroid responsive element will respond
specific example of specific transcription factors (2)
androgen prompter
estrogen prompter
two examples of chemical modification of RNA
%’ cappin: methylated guanine cap prevents immediate degradation
addition of poly-A-tail prevents immediate
what’s the difference between pre mRNA and mature mRNA
mature RNA is only composed of exons
what is splicing
the removal of non-coding introns
whats alternative splicing
splicing where particular exons are excluded or included
how can different mRNA (and hence proteins) be formed from the a single gene
through alternative splicing (the inclusion or exclusion of specific exons
how does a cell know where an intron starts and ends ??
intron concensus sequence
GU….AG
intron consensus sequence, GU end is called ….
AG end is called ,,,
donor site
acceptor site
what does it stand for: snRNPs
small nuclear ribonucleoproteins
what do snRNPs do?
they pull exons together, forming intronic loop which is cleaved and therefore the exons are spliced together
what is an intronic loop
loop made from the intron section of pre mRNA which is then cleaved to form mature mRNA
DNA- 4 main problems that lead to disease
- mutation in non-coding regions
- alterations in transcriptional activity
- non coding RNAs
- splice variants
how do mutations in non coding regions lead to disease
mutations in transcription factor binding sites may lead to an increase/decrease in protein production
how do non coding RNAs lead to disease
bind to complementary sequence and target mRNA for degradation which may impact the leves of protein
how can splice variants lead to disease
can cause proteins with altered functions
example of disease resulting from alternative splicing
hutchinson-guilford pregoria syndrome
