RNA and protein synthesis Flashcards
transcription is between what
DNA (template) to pre-mRNA
RNA processing is between
pre-mRNA to mRNA
translation is between
mRNA to proteins which make polypeptides
3 types of RNA
Ribosomal RNA (rRNA)
transfer RNA (tRNA)
messenger RNA (mRNA)
the 3 types of RNA is made from
DNA by DNA-dependent RNA polymersases
the RNA is made from what direction
due to DNA needing to be antiparallel the RNA is made from from DNA in 5’ to 3’ direction and the DNA is read from 3’ to 5’
the DNA template and new RNA are
antiparallel
3 stages of transcription
initiation
elongation
termination
2 steps of protein synthesis
transcription
translation
Initiation in transcription
RNA polymerase binds to DNA at the promoter
promoter
starting position
Elongation in transcription (look at next slide and understand diagram)
RNA nucleotides added to the 3’ end of RNA
termination in transcription
stop sequence at end of gene
precursor mRNA
orig. mRNA transcript (pre-mRNA) (or rough draft)
enzymes adds what at the end of a precursor mRNA
adds cap ot 5’ end of mRNA
why are caps needed for precursor mRNA
need cap for eukaryotic ribosome to bind
may protect degradation
what gets added at the 3’ end of precursor mRNA
polyadenylated tail (poly-a)
poly-a
when transcript complete,enzymes in nucleus recognize polyadenylation signal and cut mRNA at that site
how does poly-a help
export mRNA from nucleus ,fight degradation,make translation initiation more efficient
interrupted coding sequences
long sequences of bases in the protein-coding sequences of the gene that do not code for AA in the final protein product which are called INTRONS
introns are
noncoding regions
Exons
(expressed sequences)-part of the protien-coding sequence
Introns are removed and splice exons together
cont.coding sequence
splicesomes
variety of proteins and many snRNPs that recognize splice sites
small nuclear ribonucleoprotien complexes (snRNP)
bind to introns and catalyze the excision and splicing reactions
ribozymes
catalytic RNA molecules function as enzymes and can splice RNA
how are introns cut out
loops are made
some introns
regulate gene expression
some genes encode more
than 1 kind of polypeptide
so number of different proteins an organism can produce is much
greater than its number of genes
