Define transformation. Transformation (Griffith + Bacterial Genetics)
Transformation is the process by which a non-virulent bacterium takes up genetic material from its environment and is permanently genetically altered.
What biological mechanism allows transformation to occur?
Competent bacteria internalize extracellular DNA fragments, which integrate into their chromosome via recombination.
How is transformation used in biotechnology?
Scientists insert recombinant plasmids containing human genes into bacteria, which then express the encoded protein.
What question was Griffith trying to answer?
What molecule is responsible for heredity and virulence in bacteria?
Describe Griffith’s experimental design.
He injected mice with:
* Live S strain (virulent)
* Live R strain (non-virulent)
* Heat-killed S strain
* Heat-killed S + live R
What were the results of Griffith’s experiment?
Live S strain bacteria killed mice, live R strain did not, and heat-killed S strain did not; however, when live R bacteria were mixed with heat-killed S bacteria, the mice died and live S bacteria were recovered, demonstrating that a transferable “transforming principle” converted non-virulent R cells into virulent S cells.
What was Griffith’s interpretation?
A “transforming principle” from dead S cells converted R cells into virulent S cells.
How did Avery et al. expand on Griffith’s work?
They isolated cellular components and selectively destroyed DNA, RNA, or proteins using enzymes.
What was their hypothesis? Avery, MacLeod, & McCarty
If a molecule is responsible for transformation, destroying it should eliminate transformation.
What happened when DNA was destroyed with DNase?
Transformation did not occur.
What happened when RNA or proteins were destroyed?
Transformation still occurred.
Conclusion of Avery et al.?
DNA is the transforming principle and hereditary material.
What is a bacteriophage?
A virus that infects bacteria.
What did Hershey and Chase observe after infection and blending?
Radioactive DNA entered bacteria; radioactive protein remained outside.
Final Conclusion of Hershey-Chase Experiment
DNA, not protein, is the genetic material.
What are the four major structural features of DNA?
Double helix
Antiparallel strands
Complementary base pairing
Sugar-phosphate backbone
How are the DNA strands oriented?
Antiparallel (5’→3’ and 3’→5’).
Which base pairs with which?
A = T (2 H-bonds)
G ≡ C (3 H-bonds)
How does the Watson-Crick model explain replication?
Each strand serves as a template for synthesis of a new complementary strand.
What is a nucleoside?
*signaling molecule that is a precursor to nucloetide
Nitrogenous base + sugar (no phosphate).
What is a nucleotide?
Nitrogenous base + sugar + one or more phosphate groups.
What is the chemical difference between a deoxyribonucleoside and deoxyribonucleotide?
The nucleotide contains phosphate group(s); nucleoside does not.
Which bases are purines?
Adenine (A) and Guanine (G) — double ring.
Which bases are pyrimidines?
Cytosine (C), Thymine (T), Uracil (U) — single ring.
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Topic 1 - Introduction3
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Topic 2 - Core Concepts70
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Topic 3 - Linkage & Mapping34
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Topic 4 - Cytogenetics77
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Topic 5 - DNA Structure37
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Topic 6 - DNA Replication57
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Topic 7 - Mutations & Repair Unit 172
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Topic 7 - Mutation & Repair Unit 2 Only29
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Topic 8 - Gene Expression94
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Topic 9 - Epigenetics97
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Topic 10 - Genetics of Cancer104
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Topic 11 - Prenatal Development84
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Topic 12 - Evolutionary Development30
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Lab 1 - Isolation of Nucleic Acids39
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Lab 2 - Linkage and the Chromosomal Basis of Heredity23
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Lab 3 - Cytogenetics: Analyzing Karyotpes42
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Lab 4 - UV Mutagenesis & DNA Repair47
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Lab 5 - Pedigree Analysis & Genetic Counseling29
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Lab 6 - RFLP Analysis & DNA Fingerprinting0
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Lab 7 - Introduction to Bioinformatics0
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Lab 8 - Cancer Genetics0
