Questions and Answers
What methodology did Griffith use in his experiments?
What was the conclusion of Griffith's experiments?
Genetic material could be transferred between living organisms.
What methodology did Avery, MacLeod, and McCarty use in their research?
They destroyed various components to identify genetic material.
What was the conclusion of Avery, MacLeod, and McCarty's experiments?
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What methodology did Chargaff use in his studies?
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What conclusion did Chargaff draw from his findings?
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What methodology did Hershey and Chase use in their experiments?
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What was the conclusion of Hershey and Chase's experiments?
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Define genetic material.
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What is meant by transformation in molecular biology?
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What are bacterial colonies?
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What is a bacteriophage?
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Define radioisotopes.
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What is semi-conservative replication?
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What is gene expression?
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What does the central dogma of biology explain?
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What are parts of the central dogma of biology that are no longer true?
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Study Notes
Griffith's Experiment Methodology
- Used pneumococcus colonies: R strain (benign) and S strain (lethal).
- Injection of living S into a mouse resulted in death; living R resulted in survival; heat-killed S (HK S) also resulted in survival.
- Injection of living R combined with HK S led to mouse death, indicating transformation.
Griffith's Experiment Conclusion
- Demonstrated genetic material could be transferred between organisms, enabling new traits.
Avery, MacLeod, and McCarty's Methodology
- Investigated the genetic material by destroying cellular components: carbohydrates, lipids, proteins, and nucleic acids.
- Specific treatments used: protease (destroys proteins), ribonuclease (destroys RNA), deoxyribonuclease (destroys DNA).
- Failure to transform R cells to S cells occurred when DNA was absent.
Avery, MacLeod, and McCarty's Conclusion
- Provided evidence that DNA is the genetic material; destruction of DNA prevented genetic transfer.
- Despite evidence, skepticism remained due to misunderstanding DNA's structure and its limited combinations.
Chargaff's Methodology
- Analyzed nucleotide composition across various organisms.
Chargaff's Conclusion
- Found that in any DNA sample: [A] = [T] and [G] = [C].
- Concentrations of the four bases are not necessarily equal.
Hershey and Chase's Methodology
- Labeled bacteriophage components using radioisotopes: proteins with radioactive sulfur, DNA with radioactive phosphorus.
- Injected labeled phages into bacteria, disrupted phage particles, and centrifuged to isolate genetic material.
Hershey and Chase's Conclusion
- Established that only phosphorus (DNA) is required for new phage production, confirming DNA as genetic material.
- Demonstrated radioactive DNA is inheritably passed from parent to progeny.
Genetic Material
- Refers to the set of instructions in a cell that governs an organism's characteristics and functions.
Transformation
- A process where one bacterial strain is altered by gene transfer from another bacterial strain.
Bacterial Colonies
- Created by adding bacteria to a petri dish where they grow and multiply, with each colony originating from a single cell.
Bacteriophage
- Type of virus that specifically infects bacteria.
Radioisotopes
- Isotopes with unstable nuclei that undergo radioactive decay.
Semi-Conservative Replication
- Each new DNA double helix consists of one original strand and one newly synthesized strand.
Gene Expression
- The process of converting gene information into messenger RNA and subsequently into a functional protein.
Central Dogma of Biology
- Describes the flow of genetic information: DNA replication by DNA polymerase, transcription by RNA polymerase, and translation by ribosomes to produce proteins.
Revision of Central Dogma
- Acknowledged that not all RNAs encode proteins; includes concepts like reverse transcription and self-replicating proteins (prions).
- Some viruses utilize RNA as their genetic material, expanding previous understandings.
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Description
Explore the key experiments by Griffith and the subsequent work by Avery, MacLeod, and McCarty that laid the foundation for understanding DNA as genetic material. This quiz covers methodologies, conclusions, and the implications of their findings in genetic research.
