BSCI330 the central dogma - transcription Flashcards
how does DNA become useful
genetic info is stored in DNA in nucleus and has to be converted to proteins in the cytosol to be useful
where are mRNA molecules exported to from the nucleus
to the cytosol, where they’re translated into proteins by ribosomes
what is the central dogma information content
DNA to mRNA to protein
what is a case where the central dogma doesn’t apply
telomerase - part RNA, part protein. RNA encodes the information and is the template - goes DNA, RNA, DNA
what does RNA transcription do
generates a single-stranded RNA molecule that is complementary to the DNA template strand, except U instead of T
how is RNA synthesized and how is DNA read
RNA is synthesized 5’-3’ (each new nucleotide is added on 3’ end) by RNA polymerase
DNA is read 3’-5’
how many RNA polymerases are there in eukaryotes
3 - they synthesize different types of RNAs
where does transcription initiate
special DNA sequences called promoters
how is a promoter recognized in eukaryotes
there is a series of general transcription factors which recognize specific sequences in the promoter, bind there, and recruit the RNA polymerase to the DNA at that site
how is a promoter recognized in prokaryotes
the promoter sequence is recognized by RNA polymerase protein
how is DNA packaged in eukaryotes
DNA is packaged into chromatin and isn’t readily accessible, so needs to be opened up
what do elongation factors do
extend the RNA chain - they use ATP hydrolysis to help RNA polymerase move along the DNA
when does RNA transcription stop in prokaryotes
terminator sequence - can then be translated
when does RNA transcription stop in eukaryotes
polyadenylation signal - RNA has to be complete and exported from nucleus before being translated - requires post-transcriptional processing
what is mRNA processing
as soon as 5’ end is visible outside of RNA it is modified to have a nucleotide attached to it (the 5’ cap). Marks RNA as being mRNA-to-be
what are introns
intervening sequences
what are exons
expressed sequences
how do you remove introns
RNA splicing - cut out by spliceosome
what is the spliceosome made of
snRNPs and snRNAs and proteins, directions by RNA sequences found at intron-exon boundaries
why don’t we get immediate splicing
spliceosome assemble on pre-mRNA while it’s still being transcribed
what happens once transcription is complete
poly-A tail is added to RNA 3’ end
how does the poly-A tail work
the RNA polymerase transcribes through a specific sequence that is recognized by complex that adds the poly-A and chops off the mRNA at the sequence and adds about 200 A’s by poly-A polymerase
grabs onto RNA to signify transcription is done and can be recognized for export and translation in cytosol
where does RNA synthesis and processing occur
nucleus
where does protein synthesis occur
cytosol
