mRNA
carries genetic info to cytoplasm
relatively unstable
rRNA
structural and catalytic role
tRNA
help convert DNA language to amino acid language
Small interfering (siRNA)
man made or in virus
reduces gene expression
MicroRNA (miRNA)
genome encodes hundreds of tiny microRNAs, we don’t know what they do
small nuclear RNA (snRNA); Small nucleolar RNA (snoRNA)
stays in nucleus, never in cytoplasm
what is transcription
RNA synthesis from DNA template
what does RNA polymerase do?
bind to sites on DNA call promoters before starting transcription (can’t recognize promoters on their own and require help of other proteins- transcription factors)
what direction does polymerase move?
3’->5’ laying down complimentary RNA in 5’->3’ direction
how many types of RNA polymerase does E. coli have?
1
where are consensus sequences found?
just upstream from many bacterial genes
ribosomal RNA (rRNA)
> 80% of cell RNA
-5.8S 28S synthesized by RNA polymerase I in nucleolus
-5S RNA synthesize outside nucleolus by RNA polymerase III
Transfer RNA (tRNA)
50 tRNAs in plant and animal cells
transcribed by polymerase III
What does RNA polymerase II synthesize?
all eukaryotic mRNA precursors
What does initiation of transcription by polymerase II occur in cooperation with
a number of general transcription factors (GTFs)
what can damage DNA
ionizing radiation
exposure to a variety of reactive chemicals (alter DNA base structure)
UV radiation
nucleotide excision repair
removes thymine dimers and large chemical adducts, dna helicase and polymerase are involved
base excision repair
uses glycosylase enzymes to remove abnormal bases
