Chapter 12: Protein Synthesis What is DNA? What is DNA?

–The DNA of the gene is transcribed into RNA Which is translated into protein The flow of genetic information from DNA to RNA to Protein is called the CENTRAL DOGMA DNA Transcription RNA Protein Translation Chapter 13 Protein Synthesis - Overview

Central Dogma - FLOW IS FROM DNA TO RNA TO PROTEIN Chapter 12 Protein Synthesis (Overview)

FLOW IS FROM DNA TO RNA TO PROTEIN Genes on DNA are expressed through proteins, which provide the molecular basis for inherited traits A particular gene, is a linear sequence of many nucleotides –Specifies a polypeptide (long protein made of amino acids) Chapter 13 Protein Synthesis (Overview)

Genes - discrete units of hereditary information comprised of a nucleotide sequence found in a DNA molecule. Chapter 12 Protein Synthesis (Overview)

12.1 RNA Three Types of RNA Messenger RNA (mRNA) – carries copies of genes (DNA) to the rest of the cell. Ribosomal RNA (rRNA) – make up the ribosomes. Transfer RNA (tRNA) – transfers the amino acids to the ribosomes as specified by the mRNA

12-1 Messenger (mRNA) 1.Three main differences between mRNA and DNA Ribose instead of deoxyribose mRNA is single stranded mRNA has uracil in place of thymine (U instead of T)

12.1 TRANSCRIPTION: The process of making mRNA from DNA –Why do you need this process? Location of DNA? Nucleus Location of Ribosome? Cytoplasm –mRNA takes code from DNA in the nucleus to the cytoplasm TA CTTCAAAATC AT GAAGTTTTAG AU G AAGU UUUAG Transcription Translation RNA DNA Met LysPhePolypeptide Start condon Stop condon Strand to be transcribed

Transcription produces genetic messages in the form of mRNA 12.1 In the nucleus, the DNA helix unzips And RNA polymerase lines up nucleotides along one strand of the DNA, following the base pairing rules –As the single-stranded messenger RNA (mRNA) peels away from the gene The DNA strands rejoin RNA polymerase RNA nucleotides Direction of transcription Template Strand of DNA Newly made RNA T C A T CC A A T T G G C C A A TT GGAT G U C AUCCA A U

12.1 Eukaryotic mRNA is processed before leaving the nucleus –Noncoding segments called introns are spliced out leaving only the coding exons A 5’ cap and a poly A tail are added to the ends of mRNA Cap and tail protect mRNA Exon Intron Exon Intron Exon DNA Cap Transcription Addition of cap and tail RNA transcript with cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence Nucleus Cytoplasm 5’3’

Direction of transcription T C A T CC A A T T G G C C A A TT GGAT G U C AUCCA A U

12-3 Protein Synthesis - Translation Translation is defined as going from mRNA to protein –tRNA which have amino acids attached are going to the ribosome in the cytoplasm. What are amino acids? monomers of proteins Does the order of amino acids matter? Yes, they must be in order for the protein to fold correctly. Amino acid attachment site

–How does the correct tRNA (with amino acid attached) bind to the mRNA? The tRNA contains an anticodon which matches up with the mRNA sequence (codon). Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Amino acid attachment site Transfer RNA (tRNA) molecules serve as interpreters during translation

Ribosomes build polypeptides (proteins) –A ribosome consists of two subunits Each made up of proteins and a kind of RNA called ribosomal RNA Translation at Ribosome tRNA molecules mRNA Small subunit Growing polypeptide Large subunit 12.3 Translation

–The subunits of a ribosome Hold the tRNA and mRNA close together during translation 12.3 Translation Met Initiator tRNA 1 2 mRNA Small ribosomal subunit Start codon Large ribosomal subunit A site U A CA U C A U G P site

Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation –Once initiation is complete amino acids are added one by one to the first amino acid –The mRNA moves a codon at a time A tRNA with a complementary anticodon pairs with each codon, adding its amino acid to the peptide chain

Animation 1.Take the DNA and transcribe it into mRNA Example: TAC ATA CTA GCG ACT mRNA: 2.Take the mRNA sequence and decode it using the codon chart. AUGUAUGAUCGCUGA AUG = MET UAU = TYR GAU = ASP CGC = ARG Figure out the exact sequence of amino acids needed