Great Ideas in Science PROV 301-001 (Spring 2017) Prof. Robert M. Hazen Office: East 202 Phone: x 32163 E-mail: rhazen@ciw.edu

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

Key Idea 1. DNA carries the genetic message. 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. The ribosome assembles a protein.

Classical Genetics Gregor Mendel used 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 provide genetic clues. Humans have 23 pairs of chromosomes. In mitosis one cell becomes two: 2 daughter cells are the same as the parent. Most cells divide by mitosis in your body. In meiosis one cell becomes 4 gametes. Crossing-over shuffles genes from parents. Recombination makes every gamete unique.

Mitosis Simple cell division: A 3-step process: One cell becomes two. First copy the chromosomes. Second, separate chromosomes. Third, divide the cell into two.

Meiosis Chromosome crossover mixes up genes. 1 cell forms 4 gametes: Gametes are genetically unique. They have ½ normal chromosomes

Nucleotides: The Building Blocks of Nucleic Acids 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 A—T C—G

The Replication of DNA DNA replication occurs before mitosis & meiosis. The process is simple: The DNA double helix splits down the middle. New bases bond to exposed bases. This results in two identical DNA strands.

The Replication of DNA DNA replication occurs before mitosis & meiosis. The process is simple: The DNA double helix splits down the middle. New bases bond to exposed bases. This results in two identical DNA strands.

The Replication of DNA DNA replication occurs before mitosis & meiosis. The process is simple: The DNA double helix splits down the middle. New bases bond to exposed bases. This results in two identical DNA strands.

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

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

DNA & RNA Vocabulary Nucleotide = one genetic letter – phosphate-sugar-base (A, T, C or G) Codon = one 3-letter genetic word that defines an amino acid Gene = the recipe for one protein, typically with >100 genetic words Chromosome = a genetic cookbook with thousands of protein recipes 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 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 Step 4: Amino acids link up

Genetics – Key Concepts Human genome project Viruses DNA Fingerprinting (PCR) Genetic Engineering Microbes Plants Animals/People Cancer Ethics in genetics

Human Genome Project (Our DNA) We all have 23 pairs of chromosomes with: ~ 25,000 genes (each codes for a protein) ~ 3,000,000,000 base pairs (these are the rungs of the DNA ladder)

Human Genome Project Mapping Mapping = locating the genes

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

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 Ebola HIV SARS Swine Flu

2. Viruses

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

2. Viruses Viruses are not alive and they cannot reproduce on their own. The structure is a short piece of DNA or RNA surrounded by a protein coating. How it works: It is taken into the cell. It can takes over the cell to produce more copies. It may kill the cell, or it may hide in the cell.

Viral Epidemics Treatment of Viruses: Most medications treat the symptoms, not the virus. Vaccinations are often extremely effective. Viruses evolve rapidly because the DNA/RNA easily mutates (that is, it changes).

3. DNA Fingerprinting (PCR)

3. DNA Fingerprinting DNA fingerprinting is based on each person’s unique DNA. It can be used to identify victims, criminals, or parents/children. The process involves analyzing sections of DNA and comparing with a known person of interest.

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

3. DNA Fingerprinting (PCR)

4. Genetic Engineering

4. Genetic Engineering Genetic engineering can involve inserting foreign genes or altering existing genes. The techniques commonly involve cutting and splicing pieces of DNA. Examples include insulin, agriculture, and security.

Stem Cells An embryo’s first cells can be anything. Later cells differentiate. As the embryo grows, some genes are turned on and other genes are turned off. A “stem cell” reproduces without differentiation.

Cloning: Engineering an identical individual

4. Gene Therapy

4. Gene Therapy Gene therapy involves replacing defective genes with healthy one. “In vivo” therapies use injections. “In vitro” therapies use testtubes. Among many problems, the genes are inserted randomly, so often no proteins are made. Therapeutic viruses offer an important option.

4. Viral Gene Therapy

5. Cancer

5. Cancer-A Different Kind of Genetic Disease Normal cell division is controlled, but cancer cells reproduce without restraint. Cancer arises from genetic defects, usually 3 to 6 damaged genes. Genetic defects can increase your lifetime risk of cancer to more than 80%. Most cures rely on surgery, radiation, and/or chemotherapy. For some cancers there are now gene therapies, using viruses.

6. Ethics in Genetics Who should have access to your genetic profile? Under what circumstances should genetic discrimination be allowed? 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?