RNA Synthesis Flashcards
gene expression
the process by which DNA directs the synthesis of proteins
transcription
the synthesis of RNA by copying of a DNA template
RNA polymerase
in translation, this enzyme incorporates new RNA nucleotides onto the 3’ end of a growing RNA molecule
- forms phosphodiester bonds
- follows base pairing and antiparallel rules
- does NOT require a 3’-OH to begin synthesis
promoter
specific sequence on DNA template strand where RNA polymerase binds and begins transcription
-start point is in the middle of this sequence
terminator
specific sequence of DNA where RNA polymerase falls off and ends transcription
transcription unit
a section of DNA that is transcribed into RNA
pre-mRNA
original mRNA transcript in eukaryotes; is modified to become mature mRNA before translation
introns
non-coding/INtervening sequences (don’t code for protein)
exons
coding/EXpressed sequences (code for protein)
mRNA splicing
removal of introns from pre-mRNA and joining together of exons
spliceosome
enzyme that cuts out introns from pre-mRNA and joins together exons
central dogma
the transfer of information in a cell occurs in two steps
DNA-transcription->RNA-translation->protein
translation
the synthesis of a polypeptide using the info coded in mRNA
-occurs in the cytoplasm of all eukaryotes and prokaryotes
phases of transcription
initiation (RNA polymerase binds to promoter region)
elongation (RNA polymerase unwinds DNA, new RNA nucleotides added to the 3’ end of the growing RNA strand, growing tail dissociates from the DNA template strand, DNA strands re-anneal)
termination (at terminator sequence, RNA polymerase detaches from the DNA, RNA strand dissociates from DNA and polymerase, DNA strands fully re-anneal
template strand
the strand of DNA used to synthesize RNA
-is antiparallel and complementary to the forming RNA transcript
coding strand
also called non-template strand
-will have a very similar sequence to the new RNA transcript and run in the same direction
major types of RNA
mRNA (messenger, directly transcribed into proteins)
rRNA (ribosomal) and tRNA (transfer) both involved in translation process
mRNA processing
3’-MeG cap, 5’-poly-A tail, splicing
- enhances nuclear export of transcript
- enhances ribosomal binding to transcript
- stabilizes transcript against degrading by RNAses
- cuts out non-protein-coding sequences
5’-MeG cap
- enhances export from nucleus (the protein that helps pull out the RNA recognizes it)
- RNAses that chew 5’->3’ can’t get ahold of the strand
3’-poly-A tail
- loooooong string of adenine bases
- protects mRNA from degradation by 3’->5’ RNAses by buying the ribosomes time to complete translation (think buffering)
