dna Flashcards
what is RNA
the intermediate for genes + the proteins that encode them
what is transcription
synthesis of an RNA under the direction of DNA - produces a messenger RNA (mRNA)
- DNA -> RNA
what is translation
synthesis of a polypeptide / protein under the direction of mRNA
- RNA -> PROTEIN
prokaryotes rna characteristics
- No mRNA processing
- All happens in cytosol
eukaryotes rna characteristics
- mRNA is processed
- nucleus separates transcription from translation
what are ribosomes
site of translation
what strand is used as a template to make RNA during transcription
template strand - complementary to the non-template strand
important to remember about the non-template strand
its the same sequence as the newly formed RNA (except for the substitution of uracil for thymine)
what exists instead of Thyamine in RNA
U
whats a codon
the 3 bases that are read from the mRNA to make an amino acid
- smallest uniform length that can code for all amino acids
what is the problem with genetic code
20 amino acids but only 4 RNA bases
how many possible codons are there
64 - all of these were solved in 1960s
- 61 code for amino acids
- 3 code for stop codons
whats the start codon
AUG (Met)
3 things important to know about the genetic code
- redundant - can have multiple codon over the same thing
- unambiguous
- universal
what enzyme catalyses transcription
RNA polymerase - has same base pairing rules as DNA except U substitutes T
where does RNA polymerase attach
PROMOTER
where does the end of transcription happen in prokaryotes
TERMINATOR
3 stages of transcription
- initiation
- elongation
- termination
what is initiation in transcription
- promoters signal the initiation of RNA synthesis
- TRANSCRIPTION FACTORS bring RNA polymerase to the promoter (transcription factors + RNA polymerase = TRANSCRIPTION INITIATION COMPLEX)
- a promotor element (TATA element) = crucial in newly eukaryotic genes for formation TIC
what is elongation in transcription
- RNA polymerase zips along the double helix 10-20
- transcription progresses at 40 bases/second
- a gene can be transcribed by multiple RNA polymerases at once
what is termination in transcription
- prokaryotes: transcription stops at terminator
- eukaryotes: polymerase continues beyond end of gene + the pre mRNA is cleaved off and polymerase falls off
