Three types of RNAA. messenger RNA (mRNA)B. transfer RNA (tRNA)C. ribosome RNA (rRNA)
Steps from DNA to Proteins A cooking book in French Sequence of nucleotides A cooking book in Chinese Sequence of nucleotides Sequence of amino acidsThe Central Dogma
Steps from DNA to Proteins Nuclear DNA membrane Transcription Pre-mRNA RNA Processing mRNA Ribosome Translation Protein
Transcription• Synthesize a mRNA molecule along one template strand of DNA – In nucleus – Starts at promoter (TATA region of DNA) – Ends at terminator – Need enzyme RNA polymerase – When complete, pre-mRNA is released.
DNA A T C G T A C G A A G T C T A C G G G A C T A T C G 5 3 A C G A A G U C T A G C G A T A G C A T G C T T C A G A T G C C C T mRNA RNA polymerase Direction of transcription
Transcription• Steps – DNA unzipped by RNA polymerase – RNA polymerase builds RNA by base paring RNA nucleotides to one strand of DNA – U is used instead of T – RNA is released and leaves the nucleus
Question• What would be the complementary RNA strand for the following DNA sequence?• DNA: GCGTATG RNA: CGCAUAC
Question• What is the enzyme responsible for the production of the RNA molecule?• RNA Polymerase – Separates the DNA molecule by breaking the H- bonds between the bases. – Then moves along one of the DNA strands and links RNA nucleotides together.
RNA processing Part of a DNA strand exon intron exon intron exon3’ 5’ transcription into pre-mRNA poly-A tail cap5’ 3’ snipped out intron snipped out intron 5’ 3’ mature mRNA transcript
Translation• Synthesize a polypeptide chain using the genetic code on mRNA
Translation• Key characters – 1) mRNA : provide code – 2) tRNA : bring building blocks – 3) Ribosome (rRNA) : provide site
1) mRNA• A linear sequence of nucleotides• Three nucleotides make a codon – Codon : the genetic code for a amino acid – 64 codons – AUG: start – UAA, UAG, UGA: stop
1) mRNA start codonmRNA A U G G G C U C C A U C G G C G C A U A A codon 1 codon 2 codon 3 codon 4 codon 5 codon 6 codon 7protein methionine glycine serine isoleucine glycine alanine stop codon Primary structure of a protein aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds
2) tRNA• Delivers amino acids to ribosomes• One side attached with amino acid• Another side with anticodon – Anticodon: 3 nucleotides that can pair with a codon – 20 different types of amino acids
2) tRNAamino acidattachment site methionine amino acid U A C anticodon
3) rRNA• Major component of ribosomes• Ribosome • Place where amino acids are made into proteins • Small subunit + large subunit • Large subunit has 2 sites for tRNA
3) rRNA RibosomeLargesubunit P A Site Site mRNA A U G C U A C U U C GSmall subunit
Translation• Three Steps 1. initiation: start codon (AUG) 2. elongation: 3. termination: stop codon (UAG, UAA, UGA)• Let’s make a PROTEIN!!!!.
1) Initiation aa1Largesubunit P A Site Site 1-tRNA anticodon U A C mRNA A U G C U A C U U C G codonSmall subunit
aa2 aa1 2-tRNA 1-tRNA G A Uanticodon U A C hydrogen A U G C U A C U U C G A bonds codon mRNA
2) Elongation peptide bond aa3 aa1 aa2 3-tRNA 1-tRNA 2-tRNA G A Aanticodon U A C G A U hydrogen A U G C U A C U U C G A bonds codon mRNA
aa1 peptide bond aa3 aa21-tRNAU A C 3-tRNA(leaves) 2-tRNA G A A G A U A U G C U A C U U C G A mRNA Ribosomes move over one codon
peptide bonds aa1 aa4 aa2 aa3 4-tRNA 2-tRNA 3-tRNA G C U G A U G A AA U G C U A C U U C G A A C U mRNA
peptide bonds aa1 aa4 aa2 aa32-tRNA 4-tRNAG A U(leaves) 3-tRNA G C U G A A A U G C U A C U U C G A A C U mRNA Ribosomes move over one codon
peptide bonds aa5aa1 aa2 aa4 aa3 5-tRNA U G A 3-tRNA 4-tRNA G A A G C UG C U A C U U C G A A C U mRNA
aa1 peptide bonds aa5 aa2 aa3 aa4 5-tRNA3-tRNA U G AG A A 4-tRNA G C UG C U A C U U C G A A C U mRNA Ribosomes move over one codon
3) Termination aa5 aa4 aa199 aa3 primary aa200 structureaa2 of a proteinaa1 terminator 200-tRNA or stop codonA C U C A U G U U U A G mRNA
4) End Product• The end products of protein synthesis is a primary structure of a protein. – A sequence of amino acid bonded together by peptide bonds. aa5 aa3 aa4aa2 aa199aa1 aa200
Question:• The anticodon UAC belongs to a tRNA that recognizes and binds to a particular amino acid.• What would be the DNA base code for this amino acid?
Answer:• tRNA - UAC (anticodon)• mRNA - AUG (codon)• DNA - TAC