Genetics Chapter 6 - Genetic Analysis and Mapping in Bacteria (Exam 2)

Why are Bacteria Important in Reserach?

Bacteria Helps Uncover Gene Functions and Advance Science and Medicine Because They Reproduce Quickly and are Easy to Study

What is the Adaptation Hypothesis?

Bacteria Acquire Resistance to Phages When Exposed to Them

What is Spontaneous Mutation?

Random Genetic Changes in Bacteria That Occur Naturally

What is Selection?

Selection is the Growth of Organisms Under Specific Conditions Where Only Desired Mutants Survive, and Wild Type Cells Do Not

What is a Minimal Medium?

A Type of Media That Contains Simple Nutritional Components, Supports Wild Type Growth and Auxotrophic Mutants Do Not Grow

What is a Complete Medium?

A Type of Media That Has Complete Nutritional Components and Supports Growth of Both Wild Type and Mutants

What is a Phototroph?

The Wild Type. Can Grow on Minimal Medium and Can Synthesize All Essential Compounds it Needs

What is an Auxotroph?

The Mutant. Needs Complete Medium to Grow and Cannot Synthesize Certain Essential Compounds Due to Mutation.

What are the Three Growth Phases?

1. Lag Phase

2. Log (Exponential) Phase

3. Stationary Phase

What Happens During the Lag Phase?

Cells are Metabollically Active but Not Dividing Much

What Happens During the Log Phase?

Cells Divide Rapidly, Population Grows Exponentially

What Happens During Stationary Phase?

Growth Slows and Stops Because Nutrients are Exhausted and Waste Accumulates

What is Genetic Recombination?

Genetic Recombination is the Exchange of Genetic Material Between Two DNA Molecules to Form New Combinations of Genes on a Chromosome

How Does Gene Transfer Occur Between Bacteria?

Through Vertical Gene Transfer or Horizontal Gene Transfer

What is Vertical Gene Transfer?

The Transfer of Genetic Information From Parent to Offspring

What is Horizontal Gene Transfer?

The Transfer of Genetic Material Between Bacteria of Different Species

What are Three Examples of Horizontal Gene Transfer?

Transformation, Conjugation, and Transduction

What is Transformation?

Uptake of DNA From Environment

What is Conjugation?

DNA Transfer Via Direct Contact (Pilus)

What is Transduction?

DNA Transfer Via Bacteriophages (Viruses)

What is the F Factor?

AKA Fertility Factor. A Plasmid in Bacteria That Allows Transfer of Genetic Material During Conjugation

What are F⁺ Cells?

DNA Donors, Contain F Factor, Have Pili

What are F^- Cells?

DNA Recipients, Lack F Factor

What Did the Davis U-Tube Experiment Show?

That Cell-to-Cell Contact is Needed for Conjugation to Occur

How Does Conjugation Between a F⁺ and F^- Happen?

F⁺ Cells Form a Sex Pilus to Transfer DNA to F^- Cells

What are the Mechanisms Behind Conjugation Between Cells?

1. One Strand of DNA is Nicked Out

2. DNA Polymerase Synthesizes Complementary Strand in Both Cells

3. Ligase Seals DNA, Forming Complete Circular Plasmid in Recipient

What are HFR Cells?

Special F⁺ Cells With F Factor Integrated into Chromosome

What is F’ State of a HFR Cell?

When the F Factor of a HFR Cell Detaches from the Bacterial Chromosome, the Cell Converts to a F’ State

What is a Merozygote?

The Recipient of a F’ Cell, Becomes Partially Diploid

What is Plasmid?

Small, Circular, Double-Stranded DNA Found in Bacterial Cytoplasm

What is R Plasmid?

R Plasmids Have Resistance Transfer Factors and R-Determinants Which Can Be Transferred

What is Col Plasmids?

Derived From E. Coli and Encodes Colicins (Toxic Proteins) to Kill Nearby Bacteria Without Plasmid. Not Transmissible

What are the Steps of Transformation?

1. DNA Uptake - Foreign DNA Enters the Bacterial Cell

2. Recombination - DNA Integrates into Homologous Region of Chromosome

What is Heteroduplex DNA?

Double-Stranded DNA With Mismatched Base Pairs Formed During Recombination Between a Host Strand and Mutant Strand

What is Cotransformation?

The Simultaneous Transfer of More Than 2 Genes, Usually Linked

What are Bacteriophages?

Viruses That Infect Bacteria

What is the Structure of a Bacteriophage?

• Head - DNA Packed Inside

• Tail - Contractile Sheath Around Central Core

• Tail Fibers - Bind Specifically to Bacterial Surface

What is the Lytic Cycle?

1 of 2 Phage Life Cycles Known as Virulent Phages

What are the Steps of the Lytic Cycle?

• Phage Attaches to Bacterial Surface

• Phage Injects DNA and Degrades Host DNA

• Phage DNA Replication and Protein Synthesis Occur

• Lysis: Host Cell Bursts and Phages Released to Infect New Cells

What is the Lysogenic Cycle?

1 of 2 Phage Life Cycles Known as Temperate Phages

What are the Steps of the Lysogenic Cycle?

• Phage DNA Integrates into Bacterial Chromosome Called Prophage

• Viral DNA Replicates Along With Bacterial DNA During Cell Division

  • No Lysis: Host Cell Survives, Passes Infected DNA to Daughter Cells

What is Induction?

Happens During the Lysogenic Cycle When a Bacteria is Under Stress, Can Switch to Lytic Cycle and Lead to Lysis

What is a Prophage?

A Bacteriophage Genome That Has Integrated into a Host Via Lysogenic Cycle and Silently Replicates Along With the Host DNA

What is the Formula For Calculating Phage Numbers?

Phage Concentration = (Number of Plaques × Dilution Factor)/ Volume Plated

What are the Steps of Transduction?

1. A Bacteriophage Infects a Bacterial Cell

2. Bacterial DNA Accidentally Gets Packaged into New Phage Particles

3. These Phages Infect Another Bacterium, Transferring the DNA