Transcription of genes Flashcards
what are the 3 steps of Gene transcription
-initiation
-elongation
-termination
what is initiation in transcription
binding RNA polymerase to the promoter sequence of nucleotides on the DNA molecule
-TATA box
what does initiation during transcription ensure
-selection of proper parental DNA contain info needed for making the protein
-transcription begins at the correct nucleotide
-transcription occurs in the right direction
what is the parental DNA strand also reffered to as
-antisense strand
what is the complement strand also referred to as
the sense strand
what happens during elongation in transcription
5 STEPS
-RNA polymerase works in the 5’ to 3’ direction
-adds RNA nucleotides to the 3’ OH
*ONLY ONE DNA STRAND IS TRANSCRIBED (no Okazaki fragments)
-as polymerase passes the helix reforms and mRNA seperates
-if needed polymerase can bind agin to make more RNA
-RNA polymerase proofs to make any corrections
how does termination in transcription begin
when RNA polymerase reaches a terminator sequence and detaches
what must happen after termination during transcription
modifications before leaving the nucleus
post termination during transcription what happens to pre-mRNA (5’)
-5’ end is capped with a modified G nucleotide
-polyAtail to 3’ end
-splicing of introns
post termination during transcription what happens to pre-mRNA (3’)
WHY
a polyatail (long series of nucleotides) is added
-protect finished mRNA from enzyme break down
post termination during transcription what happens during splicing
-introns are deleted
what are SnRNPs
-snurps
-small ribonucleic proteins
recognize boundary sequences between introns and exons, loop out the intron and bring together the exon
splireasome-
-enzyme protein
-removes intron from mRNA
-cleaves the intron at its ends and splices together two exons
what is alternative splicing
a single gene can be encoded for more then one protein depending on what segments are treated as exons
