Great Ideas in Science:Great Ideas in Science:Lecture 12Lecture 12

Professor Robert HazenProfessor Robert Hazen

UNIV 301UNIV 301

Great Idea: All living things share the same genetic code.

Key IdeaKey Idea All living things share the same genetic All living things share the same genetic

codecode

1. 1. DNADNA carries the genetic message carries the genetic message

2. 2. Messenger RNA Messenger RNA copies the DNAcopies the DNA

3. 3. Transfer RNA Transfer RNA holds an amino acidholds an amino acid

4. 4. Ribosomal RNA Ribosomal RNA assembles a proteinassembles a protein

Classical Classical GeneticsGenetics

Gregor Mendel uGregor Mendel used sed pea plants to pea plants to discover three laws discover three laws of inheritanceof inheritance

1. Genes exist1. Genes exist2. Each parent 2. Each parent contributes halfcontributes half

3. Some traits are 3. Some traits are dominant and some dominant and some are recessive traitsare recessive traits

Cellular Cellular GeneticsGenetics

ChromosomesChromosomes Humans have 23 pairsHumans have 23 pairs

Mitosis (one cell becomes two)Mitosis (one cell becomes two) 2 daughter cells same as parent2 daughter cells same as parent Most cellular division in your bodyMost cellular division in your body

Meiosis (one becomes 4 Meiosis (one becomes 4 gametes)gametes) Crossing-Over (reshuffle = end of Crossing-Over (reshuffle = end of

meiosis)meiosis) Recombination makes every Recombination makes every

gamete unique.gamete unique.

MitosisMitosis Simple cell divisionSimple cell division

Observe chromosomesObserve chromosomes Not for sexual Not for sexual

reproductionreproduction ProcessProcess

Copy chromosomesCopy chromosomes Separate into two cellsSeparate into two cells

MeiosisMeiosis Sexual reproductionSexual reproduction Begins like mitosisBegins like mitosis Chromosome crossoverChromosome crossover 1 cell forms 4 gametes1 cell forms 4 gametes

Gametes are genetically Gametes are genetically uniqueunique

½ normal chromosomes½ normal chromosomes

Nucleotides: The Building Nucleotides: The Building Blocks of Nucleic AcidsBlocks of Nucleic Acids

Nucleotides are made Nucleotides are made from three molecules:from three molecules:

1. Sugar1. SugarDNA: deoxyriboseDNA: deoxyriboseRNA: riboseRNA: ribose

2. Phosphate ion2. Phosphate ion3. Base 3. Base

Adenine (A)Adenine (A)Guanine (G)Guanine (G)Cytosine (C)Cytosine (C)

Thymine (T)Thymine (T)

DNADNA’’s Double Helixs Double Helix

DNA Base PairingDNA Base Pairing Adenine:ThymineAdenine:Thymine

Cytosine:GuanineCytosine:Guanine

The Replication of DNAThe Replication of DNA DNA replication occurs DNA replication occurs

before mitosis & before mitosis & meiosismeiosis

ProcessProcess DNA double helix DNA double helix

splitssplits New bases bond to New bases bond to

exposed basesexposed bases Results in two Results in two

identical DNA identical DNA strandsstrands

How Does DNA Make How Does DNA Make Protein?Protein?

Chromosomes (DNA)Chromosomes (DNA) Carry the genetic messageCarry the genetic message

Messenger RNAMessenger RNA Copies the genetic messageCopies the genetic message

Transfer RNATransfer RNA Holds an amino acidHolds an amino acid

Ribosomal RNARibosomal RNA Assembles a proteinAssembles a protein

RNA StructureRNA Structure1. Single strand of 1. Single strand of nucleotidesnucleotides

2. The sugar is 2. The sugar is riboseribose

3. Thymine is 3. Thymine is replaced by uracil replaced by uracil (U), which bonds (U), which bonds with adeninewith adenine

Synthesis of ProteinsSynthesis of ProteinsStep 1: Transcription of Step 1: Transcription of

DNADNA

Messenger RNA (mRNA)Messenger RNA (mRNA)

Synthesis of ProteinsSynthesis of ProteinsStep 2: Match tRNA to Step 2: Match tRNA to

mRNAmRNA

Transfer RNA (tRNA)Transfer RNA (tRNA)

The RibosomeThe Ribosome

The Genetic The Genetic CodeCode

Protein Synthesis Protein Synthesis SummarySummary

4. Fold the amino acid chain into a protein.

DNA & RNA VocabularyDNA & RNA Vocabulary Nucleotide Nucleotide = one genetic letter – = one genetic letter –

phosphate-sugar-base (A, T, C or G)phosphate-sugar-base (A, T, C or G) Codon Codon = one 3-letter genetic word that = one 3-letter genetic word that

defines an amino aciddefines an amino acid GeneGene = the recipe for one protein, = the recipe for one protein,

typically with >100 genetic wordstypically with >100 genetic words ChromosomeChromosome = a genetic cookbook = a genetic cookbook

with thousands of protein recipeswith thousands of protein recipes GenomeGenome = all of the genetic material of = all of the genetic material of

an organism (23 volumes for humans)an organism (23 volumes for humans)

From DNA to ProteinFrom DNA to ProteinStep 1: DNA Step 1: DNA mRNA mRNA

From DNA to ProteinFrom DNA to ProteinmRNA mRNA tRNA tRNA Amino Amino

AcidAcid

From DNA to ProteinFrom DNA to ProteinStep 2: mRNA locks Step 2: mRNA locks onto the ribosomeonto the ribosome

From DNA to ProteinFrom DNA to ProteinStep 2: mRNA locks Step 2: mRNA locks onto the ribosomeonto the ribosome

From DNA to ProteinFrom DNA to ProteinStep 3: tRNA matches Step 3: tRNA matches

mRNAmRNA

From DNA to ProteinFrom DNA to ProteinStep 4: Amino acids link upStep 4: Amino acids link up

From DNA to ProteinFrom DNA to ProteinStep 4: Amino acids link upStep 4: Amino acids link up

From DNA to ProteinFrom DNA to ProteinRecharge the tRNA with AARecharge the tRNA with AA

Genetics – Key ConceptsGenetics – Key Concepts1.1. Human genome projectHuman genome project2.2. VirusesViruses3.3. DNA Fingerprinting DNA Fingerprinting

(PCR)(PCR)4.4. Behavioral GeneticsBehavioral Genetics5.5. Genetic EngineeringGenetic Engineering

MicrobesMicrobesPlants Plants AnimalsAnimals

6.6. Gene TherapyGene Therapy7.7. CancerCancer

1.1. Human Genome ProjectHuman Genome Project(Our DNA) (Our DNA)

23 pairs of chromosomes23 pairs of chromosomes

~ 25,000 genes; each codes for a ~ 25,000 genes; each codes for a proteinprotein

~ 3,000,000,000 base pairs (rungs of ~ 3,000,000,000 base pairs (rungs of the DNA ladder)the DNA ladder)

1.1. Human Genome ProjectHuman Genome ProjectMappingMapping

Mapping = locating the genesMapping = locating the genes

1.1. Human Genome ProjectHuman Genome ProjectSequencingSequencing

Sequencing = exact sequence of A,T,C, & GSequencing = exact sequence of A,T,C, & G

1.1. Human Genome ProjectHuman Genome ProjectOther OrganismsOther Organisms

Mouse, Rat, Rabbit, Cat, DogMouse, Rat, Rabbit, Cat, Dog

Chimpanzee, Elephant, Whale, Chimpanzee, Elephant, Whale, ZebrafishZebrafish

Frog, Fly, FlatwormFrog, Fly, Flatworm

Several plantsSeveral plants

YeastYeast

Hundreds of microbes (pathogens)Hundreds of microbes (pathogens)

Thousands of virusesThousands of viruses

Mammoth!!!Mammoth!!!

Unanswered Question:Unanswered Question:Why Are Genes Expressed?Why Are Genes Expressed?

All your cells contain the same genes.All your cells contain the same genes.

But not all cells have same the But not all cells have same the function.function.

Therefore, some process must turn Therefore, some process must turn genes on and off.genes on and off.

How and why are certain genes How and why are certain genes activated?activated?

2. Viruses2. Viruses

2. Viruses2. VirusesWhat is a Virus?What is a Virus?

A virus is a loop of genetic material A virus is a loop of genetic material (DNA or RNA) wrapped in proteins(DNA or RNA) wrapped in proteins

It It ““infectsinfects”” a cell by using the a cell by using the universal genetic codeuniversal genetic code

VirusesVirusesViruses versus cells:Viruses versus cells:

Not alive, no Not alive, no metabolismmetabolism

Cannot reproduce on Cannot reproduce on ownown

StructureStructureShort DNA or RNAShort DNA or RNAProtein coatingProtein coating

How it worksHow it worksTaken into cellTaken into cellTakes over cellTakes over cellProduces more copiesProduces more copiesKills cellKills cell

Viral EpidemicsViral Epidemics

Treatment of VirusesTreatment of Viruses Cannot use medicationCannot use medication Use vaccinationUse vaccination

Viruses evolve rapidlyViruses evolve rapidly HIVHIV Influenza Influenza SARSSARS Bird fluBird flu H1N1H1N1

3. DNA Fingerprinting 3. DNA Fingerprinting (PCR)(PCR)

DNA FingerprintingDNA Fingerprinting

DNA fingerprintingDNA fingerprinting Analysis of DNA in Analysis of DNA in

human tissuehuman tissue UsesUses

identify criminals identify criminals identify victimsidentify victims paternity disputespaternity disputes

ProcessProcess Analyze DNA Analyze DNA

sections for sections for repeatsrepeats

Compare to Compare to individual of individual of interestinterest

3. DNA Fingerprinting 3. DNA Fingerprinting (PCR)(PCR)

Step 4: Repeat with 2 strands of DNA.Step 4: Repeat with 2 strands of DNA.

4. Behavioral Genetics4. Behavioral Genetics

4. Behavioral Genetics4. Behavioral GeneticsIs your personality defined by your Is your personality defined by your

genetic makeup?genetic makeup?

Study by knocking out genes.Study by knocking out genes.

Three Assumptions:Three Assumptions:1. You can quantify behavioral functions.1. You can quantify behavioral functions.

Extroversion, Neuroticism, Conscientiousness, Extroversion, Neuroticism, Conscientiousness, Agreeableness, & OpennessAgreeableness, & Openness

2. You can identify environmental factors.2. You can identify environmental factors.

3. You can do genetic tests to tell you 3. You can do genetic tests to tell you about the person.about the person.

5. Genetic Engineering5. Genetic Engineering

Genetic EngineeringGenetic Engineering Genetic engineeringGenetic engineering

Foreign genes insertedForeign genes inserted Existing genes alteredExisting genes altered

TechniqueTechnique Restriction enzymes Restriction enzymes

cut DNAcut DNA Another DNA strand Another DNA strand

bindsbinds New gene is expressedNew gene is expressed

ExamplesExamples InsulinInsulin Agriculture Agriculture ““knockoutknockout”” mice mice BioterrorismBioterrorism

Stem Cells, Cloning, and Stem Cells, Cloning, and Regenerative MedicineRegenerative Medicine

First cells can be anythingFirst cells can be anything

Later cells differentiateLater cells differentiate

Gene ControlGene Control Genes may turn on or offGenes may turn on or off Some genes are blockedSome genes are blocked

Stem Cell Line Stem Cell Line Reproduce without Reproduce without

differentiationdifferentiation

6. Gene Therapy6. Gene Therapy

6. Gene Therapy6. Gene TherapyGene therapyGene therapy

Replace defective gene Replace defective gene with healthy genewith healthy gene

In vivoIn vivo

In vitroIn vitro

ProblemsProblemsGenes are inserted Genes are inserted

randomlyrandomly

Often no proteins are Often no proteins are mademade

Therapeutic virusesTherapeutic viruses

6. Gene Therapy6. Gene Therapy

7. 7. CancerCancer

Cancer-A Different Kind of Cancer-A Different Kind of Genetic DiseaseGenetic Disease

Normal cell division is controlledNormal cell division is controlled Cancer cells reproduce without Cancer cells reproduce without

restraintrestraint Due to genetic defectDue to genetic defect Usually 5-6 damaged genesUsually 5-6 damaged genes Collection of diseasesCollection of diseases

Genetic defectsGenetic defects Increase cancer probabilityIncrease cancer probability Lifetime risk >80%Lifetime risk >80%

CureCure Surgery, radiation, chemotherapySurgery, radiation, chemotherapy Gene therapyGene therapy

7. 7. CancerCancer

P53 gene P53 gene

(and process)(and process)

Defective geneDefective gene

Gene therapyGene therapy

Ethics in GeneticsEthics in Genetics Who should have access to Who should have access to

your genetic profile?your genetic profile? Under what circumstances Under what circumstances

should genetic should genetic discrimination be allowed?discrimination be allowed?

If you could alter the genetic If you could alter the genetic makeup of your child, where makeup of your child, where would you draw the line?would you draw the line?

What limits should society What limits should society place on genetically place on genetically engineered organisms?engineered organisms?