Unit 6b - Gene to Protein Flashcards
Central Dogma
dna –> mrna –> protein
Transcription
dna => m-rna
Translation
rna => protein
One gene =
one rna molecule
DNA properties
nucleic acid composed of nucleotides
double stranded
deoxyribose
thymine
template for individual
RNA properties
nucleic acid composed of nucleotides
single stranded
ribose
uracil
many different roles
Pre-mRNA
precursor to mRNA , newly transcribed and not edited
mRNA
carries the code from dna to ribosome, for a specific amino acid
tRNA
carries a specific amino acid to ribosome based on its anticodon to mRNA codone
transcribed in the nucleus
Codon
A sequence of three consecutive nucleotides in a DNA or RNA molecule that codes for a specific amino acid.
rRNA
makes 60% of the ribosome; site of protein synthesis
RNAi
interfernce RNA; regulatory molecule
Ribozyme
RNA molecule that functions as an enzyme
Each gene , one DNA strand is the
template strand
mRNA complementary to template
—> what direction does mRNA function.
5’ => 3’
What codes for amino acids in polypeptide chain?
mRNA triplets (codons)
How many different codon combinations?
64
Redundancy
1+ codons code for each 20 amino acids
Reading frame
groups of 4; one of three possible ways of reading a nucleotide sequence
RNA polymerase
separates dna and transcribes mRNA
mRNA elongates
in 5’ => 3’ direction
Uracil replaces
thymine
RNA polymerase attaches to ..
a promoter and stops at a terminator
Initation of Transcription in Bacteria?
rna polymerase binds directly to promoter
TATA box
dna sequence (TATAAAA) upstream from promoter.
Transcription Factors
must recognize TATA box before RNA polymerase can bind to a DNA promoter
RNA polymerase in elongation ….
adds RNA nucleotides to the 3’ end of the growing chain.
As RNA polymerase moves
it untwists DNA, then rewinds it
transcribes mRNA
In termination RNA polymerase transcribes
a terminator sequence in DNA
What are Pre-mRNA additions
5’ cap and 3’ poly-A tail are added.
Splicing
introns cut out , exons joined together.
Ribosome
rRNA + proteins
Active site A
holds AA to be added
Active site P
holds growing polypeptide chain
Active site E
exit site for tRNA
Ribosomes Initiation
small subunits binds to start codon on mRNA
tRNA carrying Met attaches to P site
Ribosome Elongation: Codon Recognition
tRNA anticodon matches codon in A site
Ribosome Elongation: Peptide Bond Formation
AAs in A site forms peptide bond in P site
Ribosome Elongation: Translocation
tRNA in A site moves to P site ; tRNA in P site moves to E site (then exits)
Ribosome Termination: Stop Codon
reached and translation stops (UAG.UAA , and UGA)
Ribosome Termination: Release Factor
binds to stop codon; polypeptide is released –> ribosomal subunits dissociate (break apart)
Prokaryotes
Central dogma in cytoplasm
DNA/RNA in cytoplasm
RNA poly binds directly to promoter
Transcritption makes mRNA
No introns
Eukaryotes
Transcription in nucleus —> Translation in cytoplasm
DNA in nucleus ; RNA travels in/out of nucleus
RNA poly binds to TATA box and transcription begins
At end of transcription = pre-RNA –> RNA processing –> final mRNA
Exons and introns
