Information Transfer and Protein Synthesis Chapter 10 Pages 221 to 241 Updated March 2006 Created by C. Ippolito March 2003
The Genetic Code Chapter 10 Sections 1 – 3 Pages 222-226 Homework: Check and Challenge p. 226 Updated March 2006 Created by C. Ippolito March 2003
DNA RNA Connection DNA controls cell by protein synthesis DNA works through RNA Three kinds of RNA Messenger RNA (mRNA) – carries instructions to ribosome Transfer RNA (tRNA) – carries amino acids to ribosome Ribosomal RNA (rRNA) – forms part of the ribosome Updated March 2006
Protein Synthesis DNA controls through TWO (2) processes: Transcription – RNA synthesis – DNA acts as a template to form mRNA, tRNA, and rRNA Translation – protein synthesis – the RNA’s made by DNA interact at the ribosome to join amino acids Interactive Tutorial Link about Protein Synthesis PBS Interactive Link DNA Replication and Protein Synthesis Updated March 2006
Genetic Code 20 different amino acids Only variable in DNA are bases Bases down side of helix “code” acids Sense side – makes protein Anti-sense side –replicates How many bases name an acid? 1 base code – only 4 acids named 2 base code – (4x4) only 16 acids named 3 base code – (4x4x4) allows 64 unique names Allows duplicate words (synonyms) for acids Allows “start” and “stop” codes Updated March 2006
Cracking the Code Nirenberg Experiment NIH scientist studied process in bacteria Made mRNA of one base only “uracil” 20 test tubes – one for each amino acid Only test tube with phenylalanine formed a polypeptide Found first triplet “codon” uuu = phe Codon – 3 bases in DNA and mRNA that “names” an amino acid Experiment repeated by others to “translate” all codons Updated March 2006
The Genetic Code Is the same in ALL LIFE Note synonyms Updated March 2006
Complete Check and Challenge on page 226 Homework Complete Check and Challenge on page 226 Updated March 2006 Created by C. Ippolito March 2003
Transcription Chapter 10 Sections 4 – 6 Pages 226 – 232 Homework: Check and Challenge p. 232 Updated March 2006 Created by C. Ippolito March 2003
RNA synthesis DNA never leaves nucleus DNA directs formation of RNA’s in nucleus RNA’s are modified RNA’s move to cytosol Catalyzed by RNA polymerase Updated March 2006
Transcription RNA polymerase unzips DNA DNA template forms RNA A U, T A, G C, C G DNA sequence ATT CGC ACC TAA forms RNA sequence UAA GCG UGG AUU Updated March 2006
DNA regions Promotor – marks start of protein Coding Sequence – protein units Terminator – marks end of protein Updated March 2006
Initiation RNA polymerase binds to promotor RNA polymerase unwinds coding region of DNA exposing “sense” strand Updated March 2006
Elongation RNA made as bases are matched RNA polymerase moves down DNA adding to RNA “transcript” Updated March 2006
Termination RNA polymerase reaches end of “gene” RNA “transcript” released; RNA polymerase falls off DNA; DNA closes Updated March 2006
RNA processing Post transcription editing Introns – cut out Exons – spliced together mRNA formed from spliced exons Updated March 2006
Complete Check and Challenge on page 232 Homework Complete Check and Challenge on page 232 Updated March 2006 Created by C. Ippolito March 2003
Translation Chapter 10 Sections 7 – 10 Pages 233 – 239 Homework: Check and Challenge p. 239 Updated March 2006 Created by C. Ippolito March 2003
tRNA charging Amino acids are attached to tRNA using ATP Updated March 2006
Ribosome Composed of two subunits: Large & Small Small subunit has TWO (2) binding sites: P-site – holds tRNA which is bonded to the growing polypeptide A-site – holds tRNA with the next amino acid to be added Updated March 2006
Initiation mRNA’s “start” sequence binds to small subunit Large subunit locks on to small subunit All proteins start with a methionine-charged tRNA at the P-site Updated March 2006
Elongation Charged tRNA matches next codon at A-site Updated March 2006
Elongation Amino acid on A-site tRNA bonds to “chain” tRNA at P-site Updated March 2006
Elongation tRNA leaves P-site and tRNA at A-site moves over to P-site mRNA moves over Next codon in A-site Process repeats Updated March 2006
Termination Protein binds to “stop” codon Polypeptide released Updated March 2006
Termination Last tRNA released Ribosome separates Updated March 2006
Homework Complete Check and Challenge on page 239 And try the DNA Transcription Interactive Game Link Updated March 2006 Created by C. Ippolito March 2003