exam 1 the central dogma Flashcards
how does genetic information become useful
genetic info stored in chromosomes must be read and converted into proteins in the cytosol
what transcribes DNA-encoded info into an RNA intermediary
RNA polymerase
where do mRNA molecules get exported to
from the nucleus to the cytosol to be translated into proteins
what is the central dogma
information flow in all prokaryotes and eukaryotes proceeds DNA -> RNA -> protein
how is telomerase an exception to the central dogma
it needs a RNA template to add DNA on the end of chromosomes (says it’s the end of the chromosome), so goes DNA -> RNA -> DNA
what does RNA transcription do
generates a single-stranded RNA molecule that is complementary to the DNA template strand
how is RNA synthesized
5’->3’ by RNA polymerase
how is DNA read
3’->5’
how many RNA polymerases do eukaryotes have
3 - they all synthesize different types of RNA
what are promoters
special DNA sequences, which direct RNA to start point where transcription of RNA occurs
in prokaryotes, how does RNA polymerase interact with promoter
RNA polymerase enzyme binds strongly to the promoter sequence
in eukaryotes, how does RNA polymerase interact with promoter
transcription requires binding of general transcription factors, which recognize promoter sequences, bind to them, and recruit RNA polymerase to start transcription
what is required to fully activate transcription in eukaryotes
additional proteins are required to modify chromatin structure
what does extension of the RNA chain require
elongation factors, which use ATP to get RNA polymerase move across chromatin
when does RNA transcription stop
after RNA polymerase encounters a special DNA sequence
what is the DNA sequence in prokaryotes that stops transcription
terminator sequence
what is the DNA sequence in eukaryotes that stops transcription
reaching a polyadenylation signal
what does eukaryotic RNA need to function
post-transcriptional processing
what is the first modification that occurs for RNA-encoding proteins to be considered mRNA
addition of 7-methylguanosine cap to 5’ end of RNA, which marks it as mRNA-to-be
what are features of 7-methylguanosine cap
triphosphate brige and methylated at 7th position
what is the 5’ cap the binding site for
ribosomes
what are introns
intervening sequences that interrupt coding sequences
what are exons
expressed sequences in coding sequences
how are introns removed
RNA splicing via spliceosome, which is very flexible
what is the spliceosome made up of
snRNPs: snRNAs
= proteins
what is the spliceosome directed by
RNA sequences found at intron-exon boundaries
what happens once transcription is complete
RNA 3’ end receives a poly-A tail
when does transcription end for eukaryotes
after poly-A tail is transcribed
how does poly-A tail get transcribed
the 3’ end of the original RNA is cleaved off and 200 A’s are added by a poly-A polymerase
what does the poly-A tail mark
that it’s unbroken RNA
where does RNA synthesis and processing occur
in the nucleus
where does protein synthesis occur
in the cytosol
how does mature mRNA get exported from nucleus to cytosol
mature mRNA binds to the nuclear export receptor, which guides it through the nuclear pore complex into the cytosol
what are mRNAs
messenger RNAs; code for proteins
what are rRNAs
ribosomal RNAs; form the basic structure of the ribosome and catalyze protein synthesis
what are tRNAs
transfer RNAs; central to protein synthesis as adaptors between mRNA and amino acids
what are snRNAs
small nuclear RNAs; splicing of pre-mRNA
what is transcription
DNA -> RNA
one-to-one correspondence of subunits with minor changes (U for T)
what is translation
RNA -> proteins
totally different chemical languages: no one-to-one correspondence: 20 amino acids, only 4 bases
