Ch 12-3 Notes, part 2 The Central Dogma = Protein Synthesis

II. Genetic Code A. The CODE is located in DNA (stays in nucleus) B. The code is transcribed from ½ the DNA ladder into a single stranded RNA C. mRNA holds the code in CODONS D. A codon is three (nitrogen) bases long E. There are ________ possible combinations- (_____) Ex. DNA = T G C C A G T G G mRNA = A C G G U C A C C mRNA codons are read as = ____________ _______

1. Read from CENTER of circle out toward edges 2. What are the 2 possible Codons for phenylalanine? 3. Which AA’s Are found on The chart twice? 4. Name stop codons

D. Codons code for SPECIFIC amino acids. 1. There are _____ amino acids 2. There are _____ codons 3. Each codon represents an amino acid 4. Some amino acids have more than one codon. 5. There is one start codon- AUG which also codes for the aa – methionine ( this is usually the 1 st aa in a protein) 6. There are 3 stop codons- UAA, UAG and UGA

=Protein synthesis IN NUCLEUS IN RIBOSOME

III. Protein Synthesis-2 Parts A.TRANSCRIPTION-in the NUCLEUS A.TRANSLATION-in the RIBOSOMES (ALL OF THEM)

IV. Transcription making RNA from DNA in the nucleus A. Initiation: RNA polymerase opens up a section(Gene) of the DNA strand which is signaled with the start codon. B. Elongation: RNA nucleotides move in to make a complementary copy from DNA

NOTE*: -RNA is always single stranded and shorter than DNA because it is a complementary copy of ONLY ONE gene. -All three types of RNA are produced by transcription, we will focus on mRNA. DNADNA DNADNA mRNAmRNA t R N A Or r R N A

C. mRNA is edited 1. Introns are REMOVED a. used to be thought of as junk DNA. b. Now believed to allow cells to pick and choose which exons/genes will be transcribed, therefore which proteins are made. 2. Exons remain and are spliced together to become genes that are expressed. What do exons do? 3. Cap and tail added to finish mRNA strand Code for Genes/proteins

D. Once mRNA is edited. Transcription is finished. E. The instructions for one GENE has been copied F. mRNA can now leave the nucleus and travel to the ribosome where Translation can begin.

V. The Genetic Code A. The mRNA strand is carrying the instructions from DNA for making a protein. B. The mRNA copy is used to make proteins in the process of TRANSLATION

Part 2 of The Central Dogma VI. TRANSLATION- making proteins in the ribosome!

A.INITIATION- 1. AUG on mRNA signals the start of translation. 2. The mRNA enters the ribosome complex (ribosome + rRNA) and the first tRNA with the complementary anticodon (UAC) and amino acid (methionine) also enter the ribosome complex.

B. ELONGATION: This is when the polypeptide chain is growing 1.A second tRNA anticodon attaches to the next mRNA codon. 2. The enzyme Ribozyme catalyzes a reaction that creates a peptide bond between the first two amino acids. 3. The order of amino acids is determined by the mRNA codons, which came from DNA.

PHENYLALANINE RIBOSOME METHIONINE tRNA lysine Start codon mRNA Elongation

lysine tRNA Translation direction 4. The enzyme Ribozyme creates a new ___________ bond to attach the amino acid to the polypeptide. 5. This process continues like an assembly line as the mRNA strand moves through the ribosome complex from the 5’ to the 3’ end.

Polypeptide chain Amino acids Peptide bond leave ribosome Ribosomes are cuteRibosomes are cute 1. A stop codon signals the finished polypeptide to be released from the ribosome complex. tRNA C. Termination- The final step in protein synthesis.

2. The polypeptide may or may not join with other chains, then it begins folding into its unique 3-D shape. ** Remember there are many ribosomes in each cell, and this is occurring all the time in each of them!

VII. Proteins become either functional or structural. A. Name 3 structural proteins. B. Name 3 functional proteins.

C. What makes one protein different from another? 1. TYPES, NUMBER, and ORDER of amino acids in the chain. 3. # of Polypeptide chains of which they are composed.

4. Type of folding a. 2 folds-secondary protein b. 3 folds-tertiary protein c. 4 folds-quaternary protein

United Streaming “Messenger RNA, Transfer RNA and Protein Synthesis”

ADD TO FINAL EXAM REVIEW! INITIATION ELONGATION TERMINATION….

A. INITIATION 1. RNA POLYMERASE (RP) recognizes a promoter on the DNA sequence –PROMOTER: Nitrogen base sequence that signals the start of a gene (AUG) 2. DNA is split by RP and one strand is used as a template to build a complementary RNA

B. ELONGATION: 1. During this stage, a polypeptide is increasing in length. a. For each codon, the ribosome verifies tRNA and mRNA are complementary, and the enzyme ribozyme creates a new peptide bond to attach the amino acid to the growing peptide chain.

C. TERMINATION 1. The final step in protein synthesis. a.A stop codon signals the finished polypeptide to be released. b. The polypeptide may or may not join with other chains, then it begins folding into its unique 3-D shape