DNA & RNADNA & RNA

Chapter 12Chapter 12

ReviewReview

• Organic ChemistryOrganic Chemistry– Nucleic AcidNucleic Acid– ProteinProtein

• Cell OrganellesCell Organelles– NucleusNucleus– RibosomeRibosome

• Cell ReproductionCell Reproduction– ““S” Phase of the Cell CycleS” Phase of the Cell Cycle

DNADNA

• Deoxyribonucleic AcidDeoxyribonucleic Acid• MoleculeMolecule• Control inherited characteristicsControl inherited characteristics

The DiscoveryThe Discovery

• Griffith and TransformationGriffith and Transformation– 19281928– Experimented with bacteria that Experimented with bacteria that

cause pneumoniacause pneumonia– Discovered the molecular nature of Discovered the molecular nature of

genesgenes

• Griffith’s ExperimentGriffith’s Experiment

Heat-killed bacteria pass their disease Heat-killed bacteria pass their disease causing ability to a harmless strain.causing ability to a harmless strain.

• Avery and DNAAvery and DNA– 19441944– Repeated Griffith’s experimentRepeated Griffith’s experiment– Destroyed the DNA during the Destroyed the DNA during the

experiment experiment transformation did not transformation did not occur!occur!

• Hershey-ChaseHershey-Chase– 19521952– Studied viruses called bacteriophagesStudied viruses called bacteriophages– Used radioactive markers to determine if Used radioactive markers to determine if

the genetic material was protein or the genetic material was protein or nucleic acid nucleic acid • PhosphorusPhosphorus• SulfurSulfur

Genetic Material Genetic Material was DNAwas DNA

The Structure of DNAThe Structure of DNA

• Friedrich MiescherFriedrich Miescher– 18691869– Extraction of DNA Extraction of DNA

from white blood from white blood cellscells

• P.A. LeveneP.A. Levene– 19201920– The chemical The chemical

nature of DNAnature of DNA– DNA is a polymerDNA is a polymer

• Chargaff’s RuleChargaff’s Rule– Nucleotide relationshipNucleotide relationship– Adenine = ThymineAdenine = Thymine– Guanine = CytosineGuanine = Cytosine– Equal proportions of Equal proportions of

purines and purines and pyrimidinespyrimidines

• Rosalind FranklinRosalind Franklin– 19501950– X-ray crystallographyX-ray crystallography– diffraction pattern of diffraction pattern of

DNADNA– Clue Clue Helical Form Helical Form

James Watson James Watson • & Francis Crick& Francis Crick

– 19531953– Model constructionModel construction

• Phosphate and sugar backbonePhosphate and sugar backbone• Nitrogen base stepsNitrogen base steps• Nobel Prize! Nobel Prize!

The Double HelixThe Double Helix

The Basic Structure of The Basic Structure of DNADNA

• SugarSugar– DeoxyriboseDeoxyribose

• Phosphate groupPhosphate group– PP

• Nitrogen BasesNitrogen Bases– PurinePurine

• Adenine (A)Adenine (A) Guanine (G)Guanine (G)

– PyrimidinePyrimidine• Thymine (T)Thymine (T) Cytosine (C)Cytosine (C)

Chromosomes and DNA Chromosomes and DNA ReplicationReplication

• DNA LengthDNA Length• Chromosome StructureChromosome Structure

• DNA ReplicationDNA Replication– Molecule separates into two strandsMolecule separates into two strands– Complementary strandsComplementary strands– Base pairing rulesBase pairing rules– Each strand is a template for the new Each strand is a template for the new

strandstrand

• Meselson –Stahl Meselson –Stahl ExperimentExperiment– 19581958– Complementary Complementary

base pairingbase pairing– Semi conservative Semi conservative

replicationreplication

How Replication OccursHow Replication Occurs

1.1. Opening of the DNA double helix with Opening of the DNA double helix with HELICASEHELICASE

2.2. Assembling complementary strands Assembling complementary strands with with DNA POLYMERASEDNA POLYMERASE to 3’ end to 3’ end

3.3. Lead Side is made continuouslyLead Side is made continuously

4.4. Lag side is made by joining Okazaki Lag side is made by joining Okazaki FragmentsFragments

5.5. DNA is only made 5’ to 3’DNA is only made 5’ to 3’

Accuracy and RepairAccuracy and Repair

• 1:10,000 pairs of nucleotides1:10,000 pairs of nucleotides• 1:1,000,000 errors in completed 1:1,000,000 errors in completed

DNADNA• Proofreader and repair enzymesProofreader and repair enzymes• Damaged DNADamaged DNA

– ChemicalsChemicals– UVUV

RNA and Protein SynthesisRNA and Protein Synthesis

• The Structure of Ribonucleic AcidThe Structure of Ribonucleic Acid– Sugar – RiboseSugar – Ribose– Phosphate groupPhosphate group– Nitrogen BasesNitrogen Bases

• Adenine and UracilAdenine and Uracil• Guanine and CytosineGuanine and Cytosine

Types of RNATypes of RNA

• Messenger RNAMessenger RNA– mRNAmRNA– Template for amino acid sequenceTemplate for amino acid sequence– Single strandedSingle stranded

• Transfer RNATransfer RNA– tRNAtRNA– Transport amino acids to the ribosomesTransport amino acids to the ribosomes

• Ribosomal RNARibosomal RNA– rRNArRNA– Assist with polypeptide synthesisAssist with polypeptide synthesis

TranscriptionTranscription

1.1. RNA PolymeraseRNA Polymerase binds to DNA and binds to DNA and separates the strandsseparates the strands

2.2. Lead side of DNA serves as a Lead side of DNA serves as a template for RNAtemplate for RNA

3.3. Promoter and Termination sitesPromoter and Termination sites4.4. RNA is editedRNA is edited

- introns- introns- exons- exons

• The Genetic CodeThe Genetic Code– The language of mRNA The language of mRNA – Codons (3 mRNA bases)Codons (3 mRNA bases)

AUGCCGUUUAUGCCGUUU

TranslationTranslation

• The genetic code is transferred to an The genetic code is transferred to an amino acidamino acid– mRNA is transcribedmRNA is transcribed– mRNA attaches to ribosomemRNA attaches to ribosome– tRNA carries amino acidstRNA carries amino acids– mRNA (Codon) and tRNA (Anticodon) pair upmRNA (Codon) and tRNA (Anticodon) pair up– Peptide bonds are formed between each Peptide bonds are formed between each

amino acidamino acid– Polypeptide continues to growPolypeptide continues to grow

Create polypeptide chain

The Central DogmaThe Central Dogma

MutationsMutations

• Gene MutationsGene Mutations– PointPoint– FrameshiftFrameshift– THE CAT ATE THE RATTHE CAT ATE THE RAT

• Chromosomal MutationsChromosomal Mutations– Loss of all or part of a chromosomeLoss of all or part of a chromosome– DeletionDeletion– DuplicationDuplication– TranslocationTranslocation