Slide 1 / 157 Slide 2 / 157 New Jersey Center for Teaching and Learning Progressive Science Initiative AP BIOLOGY This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be Big Idea 3 used for any commercial purpose without the written permission of the owners. NJCTL maintains its Part A website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course November 2012 materials to parents, students and others. www.njctl.org Click to go to website: www.njctl.org Slide 3 / 157 Slide 4 / 157 Big Idea 3 The following is the AP's explanation of the second Big Idea: Big Idea 3: " Genetic information provides for continuity of life and, in most cases, this information is passed from parent to offspring via DNA. The double- stranded structure of DNA provides a simple and elegant solution for the transmission of heritable information to the next generation; by Living systems store, retrieve, using each strand as a template, existing information can be preserved and duplicated with high fidelity within the replication process. However, transmit and respond to the process of replication is imperfect, and errors occur through information essential to life chemical instability and environmental impacts... processes. Slide 5 / 157 Slide 6 / 157 Big Idea 3 Big Idea 3: Part A " Random changes in DNA nucleotide sequences lead to heritable mutations if they are not repaired. To protect against changes in the Click on the topic to go to that section original sequence, cells have multiple mechanisms to correct errors. Despite the action of repair enzymes, some mutations are not corrected and are passed to subsequent generations. Changes in a nucleotide sequence, if present in a protein-coding region, can · The Discovery of Genes change the amino acid sequence of the polypeptide. In other cases, mutations can alter levels of gene expression or simply be silent. In · Chemistry of Nucleic Acids order for information in DNA to direct cellular processes, information · Chromosomes must be transcribed (DNA→RNA) and translated(RNA→protein). The products of transcription and translation play an important role · The Cell Cycle in determining metabolism, i.e., cellular activities and phenotypes. Biotechnology makes it possible to directly engineer heritable · S-phase changes in cells to yield novel protein products. " · Mitosis
Slide 7 / 157 Slide 8 / 157 The Discovery of Genes Nucleic Acid The precipitate at the bottom of this flask is Deoxyribose Nucleic Acid. This chemical is the informational basis for all life. Its properties allow for the storage of instructions to build living things. Return to Table of Contents Slide 9 / 157 Slide 10 / 157 Nucleic Acid The Selfish Gene "Individuals are not stable things, they are Every molecule, organelle, cell, fleeting. Chromosomes too are shuffled into organ, organ system, organism oblivion, like hands of cards soon after they and population is built by this are dealt. But the cards themselves survive molecule. the shuffling. The cards are the genes. They merely change partners and march on. It is the building block of the genes that control how bodies They are the replicators and we are their are shaped and how organisms Richard Dawkins, react to environmental factors. survival machines. When we have served Evolutionary Biologist our purpose we are cast aside. But genes are and Oxford University This molecule is evolution. denizens of geological time: genes are professor. forever." Slide 11 / 157 Slide 12 / 157 Genes Live Beyond Individuals Genes live beyond individuals As an example, blue eyes are a phenotype; a physical trait, controlled by a single gene. A recent study showed that a mutation in one individual's OCA2 Today approximately 560,000,000 people have blue eyes. Each gene, which produces the pigment that gives color to eyes, created a gene for blue eyes. This occurred 8,000 years ago and the new individual carries 2 copies of the original mutation. The gene has gene was passed generation to generation. long outlived the human that it originated in.
Slide 13 / 157 Slide 14 / 157 "Standing on the Shoulders of Giants" Primary Discovery Nucleic acids were first isolated by the The proof that DNA is the carrier of genetic information involved Swiss physician Friedrich Miescher who, a number of important historical experiments. These include: in 1869, discovered a microscopic substance in the pus of discarded Griffith Transformation Experiment surgical bandages. Avery-Macleod-McCarty Experiment At the time it was an unknown cellular substance and was not considered Hershy-Chase Experiment important until many years later. Miescher's Lab where Contributions of Watson, Crick, Wilkins, and Franklin he discovered nucleic acid Slide 15 / 157 Slide 16 / 157 Griffith's Colonies Griffith and Transformation One strain grew in rough colonies and did not cause disease. The other strain grew in smooth colonies and caused disease. In 1928 British Scientist Frederick Griffith was conducting experiments with mice to determine how bacteria made people sick. Caused Griffith isolated two different strains of pneumonia bacteria disease from mice and grew the bacteria on petri dishes in the lab. Did not cause disease R strain S strain colonies colonies Slide 17 / 157 Slide 18 / 157 Mouse Mortality Mice and the 2 strains When he injected the mice with the rough (R) strain, they lived. When he injected the mice with the smooth (S) strain, they died. Heating the S strain However, when he heated the S strain of bacteria, killing killed the them, and then injected the heat-killed S strain bacteria into the bacteria and mice, they did not die. prevented them from passing disease to the mice.
Slide 19 / 157 Slide 20 / 157 Griffith: Part 2 Griffith Experiment Part 2 Griffith then mixed heat-killed disease-causing S strain bacteria with live, harmless R strain bacteria and injected this mixture into mice. Before neither heat-killed S strain or live R strain bacteria made the mice sick, but the mixture of the two caused the mice to develop pneumonia and die. Slide 21 / 157 Slide 22 / 157 What was the chemical factor? The Search for Genes In Griffith's experiment why does the dead mouse contain living S strain when only dead S strain was injected? Theorize what may be happening. He also noted this factor was passed Griffith's conclusion: Living R strain absorbs a chemical left on as the from the dead S strain. This chemical transforms the living bacteria bacteria into the deadly S strain. reproduced. What we know now: Bacteria is capable of transformation . This is when DNA is taken in from the environment and incorporated into the bacteria's DNA. In this case the gene that produces the deadly toxin is absorbed. Slide 23 / 157 Slide 24 / 157 1 What is bacterial transformation? 2 Why was Griffith's experiment significant? The inheritance of genetic material A It showed that a chemical factor transformed A R strain bacteria into S strain bacteria The exchange of genetic material between B strains of bacteria It proved dead bacteria could still transmit B disease directly to mice The interaction between strains of bacteria C It indicated proteins were the source of The passage of genetic material from parent C D genetic material to offpsring None of the above D
Slide 25 / 157 Slide 26 / 157 Closing in on the Genetic Material Closing in on the Genetic Material After Griffith's experiment most scientists believed that the Avery used a test tube molecule transforming bacteria was a protein, not a nucleic assay. This is when a acid. scientist compares differences in test tubes after In the early 1940s experiments performed by Oswald T. treating each differently. The Avery and his colleagues at the Rockefeller Institute for benefit is that you can Medical Research challenged that assumption. discover more specific reactions. This approach will lead to more information than dead or living mice can provide. Slide 27 / 157 Slide 28 / 157 Closing in on the Genetic Material Closing in on the Genetic Material First he heat-killed the S strain bacteria and The precipitate contained the large organelles and proteins of the mixed it with detergent. This caused the cell. Avery isolated the lysate to use because it contained smaller bacterial cells to break apart. Their molecules that were more likely to be the genetic material. membranes lysed and spilled out the cell's contents. RNA lysate The upper portion of the test tube, the lysate , contains less dense materials like proteins, Proteins lysate enzymes, and nucleic acids. precipitate DNA lysate precipitate Slide 29 / 157 Slide 30 / 157 Closing in on the Genetic Material Closing in on the Genetic Material It is easy to tell the difference from R and S because they look To be sure he took the S strain lysate and mixed it with R strain to different when grown on a petri dish. (R for rough edge; S for see if it would transform the bacteria to S strain and it worked. smooth edge). lysate R strain R strain S strain S strain
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