BIOL 223 Topic 2 - Microbes and Society: Microbial Genetics and Genetic Engineering

Flashcards covering key concepts from Microbial Genetics and Genetic Engineering, including bacterial genomes, horizontal gene transfer, viruses, genetic information flow, and genetic engineering tools and applications.

What are the two main components of the bacterial genome?

A mostly single, circular DNA molecule (the chromosome) and small, independently replicating circular DNA molecules (plasmids).

What are two primary mechanisms of genetic change in bacteria?

Mutation and horizontal gene transfer.

What are three advantages of using bacteria and viruses for genetic studies?

Rapid reproduction, many progeny, haploid genome allows direct expression of mutations, asexual reproduction simplifies isolation of pure strains, easy growth in lab, small genomes, available gene manipulation techniques, medical importance, and potential for genetic engineering to produce commercial substances.

What is horizontal gene transfer?

The transfer of genetic material between independent organisms, typically within the same generation, as opposed to vertical transmission to the next generation.

Define the three main mechanisms of horizontal gene transfer in bacteria.

Conjugation: direct transfer of DNA from one bacterium to another via a cytoplasmic bridge; Transformation: bacterium takes up free DNA from its environment; Transduction: bacterial viruses (bacteriophages) transfer DNA from one bacterium to another.

What are viruses' general characteristics?

They are obligate intracellular parasites, very small with extreme genetic simplicity, contain either DNA or RNA, lack ribosomes and ATP-generating mechanisms, replicate via disassembly and reassembly, and have a specific host range.

How are viruses cultivated in the lab?

Bacteriophages can be grown in bacteria; animal viruses can be grown in intact animals, embryonated eggs, or tissue culture (in vitro monolayer).

Which type of virus typically has the highest mutation rate?

Single-stranded RNA viruses.

Describe the central dogma of genetic information flow in cells.

Genetic information flows from DNA to RNA (Transcription) and then from RNA to protein (Translation). Some viruses can perform reverse transcription (RNA to DNA).

What is the role of messenger RNA (mRNA) in protein synthesis?

mRNA carries the instructions for making proteins from the DNA.

What is recombinant DNA?

DNA that contains genetic material from more than one organism, created by joining DNA segments from different sources.

What are genetically modified organisms (GMOs)?

Organisms whose DNA has been directly manipulated or altered through genetic engineering, often by incorporating recombinant DNA, to give them new traits.

What are restriction enzymes and what is their function in genetic engineering?

Restriction enzymes are bacterial 'molecular scissors' that cut DNA at specific palindromic sequences (restriction sites), creating either sticky or blunt ends. They are crucial for cutting genes from one organism and vectors (like plasmids) to allow for gene cloning.

What enzyme 'glues' DNA fragments together in genetic engineering?

DNA ligase.

Why are bacteria often used in genetic engineering?

They are one-celled organisms, reproduce rapidly by binary fission, are easy and fast to grow, and can carry plasmids which are important tools for carrying and replicating foreign DNA.

What human products can be mass-produced using genetically engineered bacteria?

Human insulin (for diabetes) and human growth hormone (for stunted growth) are common examples.

What is Polymerase Chain Reaction (PCR)?

An enzymatic method used to make multiple copies of a specific piece of DNA, allowing for amplification to detectable levels, gene cloning, DNA sequencing, disease diagnosis, and pathogen detection.

What are the three main steps in a single PCR cycle?

Denaturing (heating to separate DNA strands), Annealing (cooling to allow primers to bind to the template DNA), and Extension (Taq Polymerase synthesizes new DNA strands).

What is the purpose of gel electrophoresis?

A technique used to separate DNA fragments based on their size (and charge), allowing for visualization and analysis of DNA.

How does gel electrophoresis separate DNA fragments?

DNA fragments, being negatively charged, migrate through an agarose gel towards the positive electrode. Smaller fragments move faster and further down the gel than larger fragments.

Who proposed the Three Domain system of classification using rRNA gene sequences?

Carl Woese.

Why are rRNA gene sequences commonly used for taxonomic classification and phylogenetic studies?

rRNA is a vital, conserved molecule present in all known life forms. Its sequences contain both highly conserved and variable regions, allowing for comparison across different evolutionary distances. Prokaryotic and Eukaryotic ribosomes also have distinct rRNA subunits (e.g., 16S RNA in 30S prokaryotic subunit, 18S RNA in 40S eukaryotic subunit).

What are the two main components of the bacterial genome?

A mostly single, circular DNA molecule (the chromosome) and small, independently replicating circular DNA molecules (plasmids).

What are two primary mechanisms of genetic change in bacteria?

Mutation and horizontal gene transfer.

What are three advantages of using bacteria and viruses for genetic studies?

Rapid reproduction, many progeny, haploid genome allows direct expression of mutations, asexual reproduction simplifies isolation of pure strains, easy growth in lab, small genomes, available gene manipulation techniques, medical importance, and potential for genetic engineering to produce commercial substances.

What is horizontal gene transfer?

The transfer of genetic material between independent organisms, typically within the same generation, as opposed to vertical transmission to the next generation.

Define the three main mechanisms of horizontal gene transfer in bacteria.

Conjugation: direct transfer of DNA from one bacterium to another via a cytoplasmic bridge; Transformation: bacterium takes up free DNA from its environment; Transduction: bacterial viruses (bacteriophages) transfer DNA from one bacterium to another.

What are viruses' general characteristics?

They are obligate intracellular parasites, very small with extreme genetic simplicity, contain either DNA or RNA, lack ribosomes and ATP-generating mechanisms, replicate via disassembly and reassembly, and have a specific host range.

How are viruses cultivated in the lab?

Bacteriophages can be grown in bacteria; animal viruses can be grown in intact animals, embryonated eggs, or tissue culture (in vitro monolayer).

Which type of virus typically has the highest mutation rate?

Single-stranded RNA viruses.

Describe the central dogma of genetic information flow in cells.

Genetic information flows from DNA to RNA (Transcription) and then from RNA to protein (Translation). Some viruses can perform reverse transcription (RNA to DNA).

What is the role of messenger RNA (mRNA) in protein synthesis?

mRNA carries the instructions for making proteins from the DNA.

What is recombinant DNA?

DNA that contains genetic material from more than one organism, created by joining DNA segments from different sources.

What are genetically modified organisms (GMOs)?

Organisms whose DNA has been directly manipulated or altered through genetic engineering, often by incorporating recombinant DNA, to give them new traits.

What are restriction enzymes and what is their function in genetic engineering?

Restriction enzymes are bacterial 'molecular scissors' that cut DNA at specific palindromic sequences (restriction sites), creating either sticky or blunt ends. They are crucial for cutting genes from one organism and vectors (like plasmids) to allow for gene cloning.

What enzyme 'glues' DNA fragments together in genetic engineering?

DNA ligase.

Why are bacteria often used in genetic engineering?

They are one-celled organisms, reproduce rapidly by binary fission, are easy and fast to grow, and can carry plasmids which are important tools for carrying and replicating foreign DNA.

What human products can be mass-produced using genetically engineered bacteria?

Human insulin (for diabetes) and human growth hormone (for stunted growth) are common examples.

What is Polymerase Chain Reaction (PCR)?

An enzymatic method used to make multiple copies of a specific piece of DNA, allowing for amplification to detectable levels, gene cloning, DNA sequencing, disease diagnosis, and pathogen detection.

What are the three main steps in a single PCR cycle?

Denaturing (heating to separate DNA strands), Annealing (cooling to allow primers to bind to the template DNA), and Extension (Taq Polymerase synthesizes new DNA strands).

What is the purpose of gel electrophoresis?

A technique used to separate DNA fragments based on their size (and charge), allowing for visualization and analysis of DNA.

How does gel electrophoresis separate DNA fragments?

DNA fragments, being negatively charged, migrate through an agarose gel towards the positive electrode. Smaller fragments move faster and further down the gel than larger fragments.

Who proposed the Three Domain system of classification using rRNA gene sequences?

Carl Woese.

Why are rRNA gene sequences commonly used for taxonomic classification and phylogenetic studies?

rRNA is a vital, conserved molecule present in all known life forms. Its sequences contain both highly conserved and variable regions, allowing for comparison across different evolutionary distances.

What are the two main reproductive cycles of bacteriophages?

The lytic cycle (virulent phages replicate and lyse host cells) and the lysogenic cycle (temperate phages integrate their DNA into the host genome, replicating with it, and can later enter the lytic cycle).

What are the main stages of the lytic cycle in bacteriophages?

1. Attachment: Phage binds to host cell.

2. Penetration: Phage injects its genetic material into the cell.

3. Biosynthesis: Host cell's machinery is used to make phage DNA and proteins.

4. Maturation: New phage particles are assembled.

5. Release: Host cell lyses, releasing new phages.

What is 'heat shock' in the context of bacterial genetic engineering?

A common laboratory technique used to increase the permeability of bacterial cell membranes, facilitating the uptake of foreign DNA (e.g., plasmids) during transformation.

How does heat shock promote bacterial transformation?

It creates temporary pores in the bacterial cell wall and membrane, allowing DNA molecules to enter the cell more easily. This is often preceded by treatment with calcium chloride (CaCl_2) to neutralize DNA's negative charge and shield membrane charges, further aiding DNA entry.