EUKARYOTIC TRANSCRIPTION Flashcards
regions in mature mRNA is found in the gene for the mRNA
start codon, leader sequence, exon
poly A end of eukaryotic mRNA originate from
sequential addition of A residues at the 3’ end of primary transcript
eukaryotic mRNA
- contain a poly A tail upto 250 residue
- primary nuclear transcripts are much larger than the cytoplasmic mRNA
- a guanosine residue is attached to the 5’ terminus in an unusual 5’-5’ linkage
purpose of storing information in exon separated by intron
eukaryotes are able to then use the information in one DNA sequence in alternative ways
spliceosome mediated splicing of GU-AG intron
require ATP, involve transesterification reaction, involves the nucleophilic attack on the OH group on the sugar phosphate backbone
snRNA
snRNA are strictly localized to the nucleus, most snRNAs are very abundant, some snRNAs can base pair with the intron consensus sequence
introns are released as lariats during splicing of
pre- mRNA transcripts and group II intron containing transcripts
alternating splicing means that
the same gene can code for several different proteins
splicing event the intermediate do not form the lariat or the branched structure
group I intron splicing and hnRNA splicing
introns in tRNA
GMP, GDP, GTP
in mammalian cells, RNA editing
can change the coding capacity of a gene after transcription, creates a stop codon in the middle of the apo-B- mRNA in intestinal cells but not in liver cells, can change specific nucleotides by deamination
foot printing assay can be used to
determine the DNA binding site for the transcription factor
post- transcriptional modifications involves
splicing, 5’ capping, 3’ polyadenylation