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Questions and Answers
Who discovered PCR and when?
Who discovered PCR and when?
Kary B. Mullis in 1983
Two sections of double stranded DNA cut by the same restriction enzyme will likely anneal naturally (on their own).
Two sections of double stranded DNA cut by the same restriction enzyme will likely anneal naturally (on their own).
True
Reverse transcriptase catalyzes reverse transcription of DNA from RNA.
Reverse transcriptase catalyzes reverse transcription of DNA from RNA.
True
What are the 3 types of horizontal gene transfer among prokaryotes?
What are the 3 types of horizontal gene transfer among prokaryotes?
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During bacterial conjugation, which cell initiates contact via a pilus?
During bacterial conjugation, which cell initiates contact via a pilus?
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Virulent phages integrate their genetic material into a bacterial cell's chromosome, and the host cell can continue to live and reproduce normally.
Virulent phages integrate their genetic material into a bacterial cell's chromosome, and the host cell can continue to live and reproduce normally.
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Viruses that only use the lytic cycle are called virulent phages.
Viruses that only use the lytic cycle are called virulent phages.
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Define/describe bacterial transformation.
Define/describe bacterial transformation.
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Describe bacterial competence in the context of transformation.
Describe bacterial competence in the context of transformation.
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Describe the 4 main conditions and outcomes of Frederick Griffith's experiment.
Describe the 4 main conditions and outcomes of Frederick Griffith's experiment.
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Frederick Griffith's experiment is a classic example of bacterial transformation.
Frederick Griffith's experiment is a classic example of bacterial transformation.
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Humans can only transfer genes vertically, while bacteria can only transfer genes horizontally.
Humans can only transfer genes vertically, while bacteria can only transfer genes horizontally.
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Phages and antibiotics are both used as broad-spectrum tools for combating bacterial infections.
Phages and antibiotics are both used as broad-spectrum tools for combating bacterial infections.
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Transduction is the transfer of DNA from one host prokaryotic bacterium to another prokaryotic bacterium via a virus capable of infecting both the donor and recipient cells.
Transduction is the transfer of DNA from one host prokaryotic bacterium to another prokaryotic bacterium via a virus capable of infecting both the donor and recipient cells.
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Describe the difference between generalized transduction and specialized transduction.
Describe the difference between generalized transduction and specialized transduction.
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During gel electrophoresis, DNA is drawn towards the negative electrode, allowing one to separate molecules based on charge, size and shape.
During gel electrophoresis, DNA is drawn towards the negative electrode, allowing one to separate molecules based on charge, size and shape.
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During gel electrophoresis, larger fragments migrate faster and farther than smaller ones through the agarose gel.
During gel electrophoresis, larger fragments migrate faster and farther than smaller ones through the agarose gel.
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In addition to DNA, PCR can be used to directly amplify RNA.
In addition to DNA, PCR can be used to directly amplify RNA.
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Study Notes
PCR and Its Discovery
- Polymerase Chain Reaction (PCR) was discovered by Kary B. Mullis in 1983, revolutionizing molecular biology techniques for amplifying DNA.
DNA Annealing and Restriction Enzymes
- Two sections of double-stranded DNA cut by the same restriction enzyme can anneal naturally but require DNA ligase to seal gaps in the phosphodiester backbone.
Reverse Transcriptase Functionality
- Reverse transcriptase catalyzes the synthesis of DNA from an RNA template, playing a crucial role in retroviral replication.
Horizontal Gene Transfer in Prokaryotes
- Three primary types of horizontal gene transfer among prokaryotes: transduction, transformation, and bacterial conjugation.
Bacterial Conjugation
- In bacterial conjugation, the donor cell is responsible for initiating the contact with the recipient cell through a specialized structure called a pilus.
Virus Life Cycles
- Virulent phages operate solely via the lytic cycle, resulting in cell lysis, while temperate phages can integrate their genetic material into the host chromosome during the lysogenic cycle.
Bacterial Transformation
- Transformation occurs when a bacterial cell captures naked or exogenous DNA from its environment, requiring the bacterium to be in a “competent state” to uptake the DNA.
Bacterial Competence
- During transformation, bacterial competence is achieved when the bacterial cell membrane and wall are made more permeable, often induced by heat-shock, to facilitate DNA uptake.
Frederick Griffith's Experiment
- Griffith's experiment uncovered key principles of bacterial transformation:
- Rough strain (non-virulent) → mouse survives
- Smooth strain (virulent) → mouse dies
- Heat-killed smooth strain → mouse survives
- Rough + heat-killed smooth strain → mouse dies
Griffith's Contributions
- Frederick Griffith's work serves as a classic illustration of bacterial transformation through the incorporation of genetic material from dead virulent bacteria by live non-virulent strains.
Gene Transfer Mechanisms
- Humans transfer genes only vertically (from parent to offspring), while bacteria can transfer genes both horizontally (across individuals) and vertically.
Phages vs. Antibiotics
- Antibiotics generally act as broad-spectrum agents against bacteria, while phages are highly specific to their target bacterial strains.
Transduction Definitions
- Transduction involves the transfer of DNA via a virus from one host bacterium to another and can occur between both prokaryotic and eukaryotic cells.
Generalized vs. Specialized Transduction
- Generalized transduction involves the random transfer of DNA segments, independent of specific sequences, whereas specialized transduction transfers specific DNA sequences along with viral DNA.
Gel Electrophoresis Mechanics
- Gel electrophoresis separates DNA molecules based on charge, size, and shape; negatively charged DNA moves toward the positive electrode, not the negative one.
Migration of DNA Fragments
- In gel electrophoresis, smaller DNA fragments migrate faster and travel farther through the agarose gel than larger fragments due to size constraints.
PCR Amplification Limitations
- PCR is designed to amplify DNA; it cannot directly amplify RNA without prior conversion to complementary DNA (cDNA).
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