Great Ideas in Science: Lecture 12 Professor Robert Hazen UNIV 301 Great Idea: All living things share the same genetic code.

Key Idea All living things share the same genetic code All living things share the same genetic code 1. DNA carries the genetic message 2. Messenger RNA copies the DNA 3. Transfer RNA holds an amino acid 4. Ribosomal RNA assembles a protein

Classical Genetics Gregor Mendel u sed pea plants to discover three laws of inheritance Gregor Mendel u sed pea plants to discover three laws of inheritance 1. Genes exist 2. Each parent contributes half 3. Some traits are dominant and some are recessive traits

Cellular Genetics Chromosomes Chromosomes Humans have 23 pairs Humans have 23 pairs Mitosis (one cell becomes two) Mitosis (one cell becomes two) 2 daughter cells same as parent 2 daughter cells same as parent Most cellular division in your body Most cellular division in your body Meiosis (one becomes 4 gametes) Meiosis (one becomes 4 gametes) Crossing-Over (reshuffle = end of meiosis) Crossing-Over (reshuffle = end of meiosis) Recombination makes every gamete unique. Recombination makes every gamete unique.

Mitosis Simple cell division Simple cell division Observe chromosomes Observe chromosomes Not for sexual reproduction Not for sexual reproduction Process Process Copy chromosomes Copy chromosomes Separate into two cells Separate into two cells

Meiosis Sexual reproduction Sexual reproduction Begins like mitosis Begins like mitosis Chromosome crossover Chromosome crossover 1 cell forms 4 gametes 1 cell forms 4 gametes Gametes are genetically unique Gametes are genetically unique ½ normal chromosomes ½ normal chromosomes

Nucleotides: The Building Blocks of Nucleic Acids Nucleotides are made from three molecules: Nucleotides are made from three molecules: 1. Sugar DNA: deoxyribose RNA: ribose 2. Phosphate ion 3. Base Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

DNA’s Double Helix

DNA Base Pairing Adenine:Thymine Adenine:ThymineCytosine:Guanine

The Replication of DNA DNA replication occurs before mitosis & meiosis DNA replication occurs before mitosis & meiosis Process Process DNA double helix splits DNA double helix splits New bases bond to exposed bases New bases bond to exposed bases Results in two identical DNA strands Results in two identical DNA strands

How Does DNA Make Protein? Chromosomes (DNA) Chromosomes (DNA) Carry the genetic message Carry the genetic message Messenger RNA Messenger RNA Copies the genetic message Copies the genetic message Transfer RNA Transfer RNA Holds an amino acid Holds an amino acid Ribosomal RNA Ribosomal RNA Assembles a protein Assembles a protein

RNA Structure 1. Single strand of nucleotides 2. The sugar is ribose 3. Thymine is replaced by uracil (U), which bonds with adenine

Synthesis of Proteins Step 1: Transcription of DNA Messenger RNA (mRNA)

Synthesis of Proteins Step 2: Match tRNA to mRNA Transfer RNA (tRNA)

The Ribosome

The Genetic Code

Protein Synthesis Summary 4. Fold the amino acid chain into a protein.

DNA & RNA Vocabulary Nucleotide = one genetic letter – phosphate-sugar-base (A, T, C or G) Nucleotide = one genetic letter – phosphate-sugar-base (A, T, C or G) Codon = one 3-letter genetic word that defines an amino acid Codon = one 3-letter genetic word that defines an amino acid Gene = the recipe for one protein, typically with >100 genetic words Gene = the recipe for one protein, typically with >100 genetic words Chromosome = a genetic cookbook with thousands of protein recipes Chromosome = a genetic cookbook with thousands of protein recipes Genome = all of the genetic material of an organism (23 volumes for humans) Genome = all of the genetic material of an organism (23 volumes for humans)

From DNA to Protein Step 1: DNA  mRNA

From DNA to Protein mRNA  tRNA  Amino Acid

From DNA to Protein Step 2: mRNA locks onto the ribosome

From DNA to Protein Step 3: tRNA matches mRNA

From DNA to Protein Step 4: Amino acids link up

From DNA to Protein Recharge the tRNA with AA

Genetics – Key Concepts 1. Human genome project 2. Viruses 3. DNA Fingerprinting (PCR) 4. Behavioral Genetics 5. Genetic Engineering MicrobesPlantsAnimals 6. Gene Therapy 7. Cancer

1.Human Genome Project (Our DNA) 23 pairs of chromosomes ~ 25,000 genes; each codes for a protein ~ 3,000,000,000 base pairs (rungs of the DNA ladder)

1.Human Genome Project Mapping Mapping = locating the genes

1.Human Genome Project Sequencing Sequencing = exact sequence of A,T,C, & G

1.Human Genome Project Other Organisms Mouse, Rat, Rabbit, Cat, Dog Chimpanzee, Elephant, Whale, Zebrafish Frog, Fly, Flatworm Several plants Yeast Hundreds of microbes (pathogens) Thousands of viruses Mammoth!!!

Unanswered Question: Why Are Genes Expressed? All your cells contain the same genes. But not all cells have same the function. Therefore, some process must turn genes on and off. How and why are certain genes activated?

2. Viruses

2. Viruses What is a Virus? A virus is a loop of genetic material (DNA or RNA) wrapped in proteins A virus is a loop of genetic material (DNA or RNA) wrapped in proteins It “infects” a cell by using the universal genetic code It “infects” a cell by using the universal genetic code

Viruses Viruses versus cells: Not alive, no metabolism Cannot reproduce on own Structure Short DNA or RNA Protein coating How it works Taken into cell Takes over cell Produces more copies Kills cell

Viral Epidemics Treatment of Viruses Treatment of Viruses Cannot use medication Cannot use medication Use vaccination Use vaccination Viruses evolve rapidly Viruses evolve rapidly HIV HIV Influenza Influenza SARS SARS Bird flu Bird flu H1N1 H1N1

3. DNA Fingerprinting (PCR)

DNA Fingerprinting DNA fingerprinting DNA fingerprinting Analysis of DNA in human tissue Analysis of DNA in human tissue Uses Uses identify criminals identify criminals identify victims identify victims paternity disputes paternity disputes Process Process Analyze DNA sections for repeats Analyze DNA sections for repeats Compare to individual of interest Compare to individual of interest

3. DNA Fingerprinting (PCR) Step 4: Repeat with 2 strands of DNA.

4. Behavioral Genetics

Is your personality defined by your genetic makeup? Study by knocking out genes. Three Assumptions: 1. You can quantify behavioral functions. Extroversion, Neuroticism, Conscientiousness, Agreeableness, & Openness 2. You can identify environmental factors. 3. You can do genetic tests to tell you about the person.

5. Genetic Engineering

Genetic Engineering Genetic engineering Genetic engineering Foreign genes inserted Foreign genes inserted Existing genes altered Existing genes altered Technique Technique Restriction enzymes cut DNA Restriction enzymes cut DNA Another DNA strand binds Another DNA strand binds New gene is expressed New gene is expressed Examples Examples Insulin Insulin Agriculture Agriculture “knockout” mice “knockout” mice Bioterrorism Bioterrorism

Stem Cells, Cloning, and Regenerative Medicine First cells can be anything First cells can be anything Later cells differentiate Later cells differentiate Gene Control Gene Control Genes may turn on or off Genes may turn on or off Some genes are blocked Some genes are blocked Stem Cell Line Stem Cell Line Reproduce without differentiation Reproduce without differentiation

6. Gene Therapy

Gene therapy Replace defective gene with healthy gene In vivo In vitro Problems Genes are inserted randomly Often no proteins are made Therapeutic viruses

6. Gene Therapy

7. Cancer

Cancer-A Different Kind of Genetic Disease Normal cell division is controlled Normal cell division is controlled Cancer cells reproduce without restraint Cancer cells reproduce without restraint Due to genetic defect Due to genetic defect Usually 5-6 damaged genes Usually 5-6 damaged genes Collection of diseases Collection of diseases Genetic defects Genetic defects Increase cancer probability Increase cancer probability Lifetime risk >80% Lifetime risk >80% Cure Cure Surgery, radiation, chemotherapy Surgery, radiation, chemotherapy Gene therapy Gene therapy

7. Cancer P53 gene P53 gene (and process) Defective gene Gene therapy

Ethics in Genetics Who should have access to your genetic profile? Who should have access to your genetic profile? Under what circumstances should genetic discrimination be allowed? Under what circumstances should genetic discrimination be allowed? If you could alter the genetic makeup of your child, where would you draw the line? If you could alter the genetic makeup of your child, where would you draw the line? What limits should society place on genetically engineered organisms? What limits should society place on genetically engineered organisms?