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Microbiology Exam 2 Study Guide: Microbial Genetics & Control of Microbial Growth

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Q1. Compare features of viral, prokaryotic, and eukaryotic genomes.

Background

Topic: Microbial Genetics

This question tests your understanding of the similarities and differences in the genetic material of viruses, prokaryotes (like bacteria), and eukaryotes (like fungi, protozoa, and animals).

Key Terms:

  • Genome: The complete set of genetic material in an organism.

  • Prokaryote: Organisms without a nucleus (e.g., bacteria).

  • Eukaryote: Organisms with a nucleus (e.g., fungi, animals).

  • Virus: Acellular infectious agents with either DNA or RNA genomes.

Step-by-Step Guidance

  1. List the main characteristics of viral genomes (e.g., type of nucleic acid, structure, size, organization).

  2. Describe the features of prokaryotic genomes (e.g., chromosome structure, plasmids, location).

  3. Outline the features of eukaryotic genomes (e.g., chromosome number, linearity, presence of introns/exons).

  4. Compare and contrast these features, focusing on differences in organization, complexity, and genetic material.

Try solving on your own before revealing the answer!

Q2. Explain how nucleic acids functivon in the storage and transfer of information.

Background

Topic: Nucleic Acid Function

This question is about how DNA and RNA store genetic information and how that information is transferred within and between cells.

Key Terms:

  • DNA: Deoxyribonucleic acid, stores genetic information.

  • RNA: Ribonucleic acid, involved in information transfer and protein synthesis.

  • Central Dogma: The flow of genetic information from DNA to RNA to protein.

Step-by-Step Guidance

  1. Describe how DNA stores genetic information in its sequence of bases.

  2. Explain the process of transcription (DNA to RNA) and translation (RNA to protein).

  3. Discuss the roles of different types of RNA in transferring information.

Try solving on your own before revealing the answer!

Q3. Describe the structure of DNA (double helix, hydrogen bonding, antiparallel, base-pairing, 5’-3’ ends, parts of a nucleotide, function).

Background

Topic: DNA Structure

This question tests your knowledge of the physical and chemical structure of DNA and its functional significance.

Key Terms and Concepts:

  • Double helix: The shape of DNA.

  • Hydrogen bonds: Hold base pairs together.

  • Antiparallel: Strands run in opposite directions (5’ to 3’ and 3’ to 5’).

  • Base-pairing: Adenine with Thymine, Guanine with Cytosine.

  • Nucleotide: Consists of a sugar, phosphate, and nitrogenous base.

Step-by-Step Guidance

  1. Draw or visualize the double helix structure and label the sugar-phosphate backbone and base pairs.

  2. Explain how hydrogen bonds form between specific base pairs (A-T, G-C).

  3. Describe what is meant by antiparallel strands and the significance of 5’ and 3’ ends.

  4. List the components of a nucleotide and their arrangement in the DNA strand.

Try solving on your own before revealing the answer!

Q4. Summarize the steps in DNA replication.

Background

Topic: DNA Replication

This question is about the process by which DNA makes a copy of itself before cell division.

Key Terms:

  • Replication fork

  • Helicase, DNA polymerase, primase, ligase

  • Leading and lagging strands

Step-by-Step Guidance

  1. Identify the enzymes involved in DNA replication and their roles.

  2. Describe how the double helix is unwound and the replication fork is formed.

  3. Explain how new nucleotides are added to the leading and lagging strands.

  4. Discuss how Okazaki fragments are joined together.

Try solving on your own before revealing the answer!

Q5. What does semi-conservative replication mean?

Background

Topic: DNA Replication Mechanism

This question tests your understanding of how DNA is copied during cell division.

Key Terms:

  • Semi-conservative: Each new DNA molecule consists of one old (parental) strand and one new strand.

Step-by-Step Guidance

  1. Define the term "semi-conservative replication" in your own words.

  2. Explain how this model was demonstrated experimentally (e.g., Meselson-Stahl experiment).

  3. Describe the significance of this process for genetic continuity.

Try solving on your own before revealing the answer!

Q6. Describe the structure of RNA (single stranded, base-pairing, function).

Background

Topic: RNA Structure and Function

This question is about the differences between RNA and DNA and the roles of RNA in the cell.

Key Terms:

  • Single-stranded

  • Ribose sugar

  • Uracil instead of Thymine

  • Types of RNA: mRNA, tRNA, rRNA

Step-by-Step Guidance

  1. Describe the basic structure of RNA and how it differs from DNA.

  2. Explain the types of base-pairing that can occur in RNA.

  3. List the main functions of RNA in the cell.

Try solving on your own before revealing the answer!

Q7. What nucleic acid base is used in the construction of RNA that is not utilized in DNA molecules?

Background

Topic: Nucleic Acid Bases

This question tests your knowledge of the differences in nitrogenous bases between DNA and RNA.

Key Terms:

  • Uracil (RNA)

  • Thymine (DNA)

Step-by-Step Guidance

  1. List the four bases found in DNA and the four bases found in RNA.

  2. Identify which base is unique to RNA and which is unique to DNA.

Try solving on your own before revealing the answer!

Q8. How is transcription similar to replication? How is it different?

Background

Topic: Transcription vs. Replication

This question asks you to compare and contrast the processes of making RNA from DNA (transcription) and copying DNA (replication).

Key Terms:

  • Template strand

  • RNA polymerase vs. DNA polymerase

  • Product: RNA vs. DNA

Step-by-Step Guidance

  1. List the similarities between transcription and replication (e.g., both use a DNA template).

  2. List the differences (e.g., enzymes involved, product, length of molecule synthesized).

  3. Explain why these differences are important for cell function.

Try solving on your own before revealing the answer!

Q9. Understand the processes of transcription & translation.

Background

Topic: Gene Expression

This question is about the steps by which genetic information is used to make proteins.

Key Terms:

  • Transcription: DNA to RNA

  • Translation: RNA to protein

  • Codon, anticodon

Step-by-Step Guidance

  1. Describe the main steps of transcription, including initiation, elongation, and termination.

  2. Outline the steps of translation, including the roles of mRNA, tRNA, and ribosomes.

  3. Explain how the genetic code is used to specify amino acids.

Try solving on your own before revealing the answer!

Q10. Describe the process of eukaryotic mRNA (exons, introns, pre-mRNA, mRNA).

Background

Topic: Eukaryotic Gene Expression

This question focuses on how eukaryotic cells process RNA transcripts before translation.

Key Terms:

  • Exon: Coding region

  • Intron: Non-coding region

  • Pre-mRNA: Initial transcript

  • mRNA: Mature messenger RNA

Step-by-Step Guidance

  1. Define exons and introns and their roles in gene structure.

  2. Describe the process of transcription producing pre-mRNA.

  3. Explain how introns are removed (splicing) and exons joined to form mature mRNA.

Try solving on your own before revealing the answer!

Q11. What types of RNA are involved in translation and what are their roles?

Background

Topic: Translation Machinery

This question is about the different RNA molecules that participate in protein synthesis.

Key Terms:

  • mRNA: Messenger RNA

  • tRNA: Transfer RNA

  • rRNA: Ribosomal RNA

Step-by-Step Guidance

  1. List the three main types of RNA involved in translation.

  2. Describe the function of each type in the process of protein synthesis.

Try solving on your own before revealing the answer!

Q12. What is the ‘triple code’? What is its role in the structure of proteins built through translation?

Background

Topic: Genetic Code

This question tests your understanding of how nucleotide sequences specify amino acids in proteins.

Key Terms:

  • Codon: Sequence of three nucleotides

  • Genetic code: Relationship between codons and amino acids

Step-by-Step Guidance

  1. Define what is meant by the "triple code" or codon.

  2. Explain how codons determine the sequence of amino acids in a protein.

  3. Discuss the importance of the reading frame in translation.

Try solving on your own before revealing the answer!

Q13. Specifically, what is a mutation?

Background

Topic: Mutations

This question is about changes in the genetic material and their consequences.

Key Terms:

  • Mutation: Change in DNA sequence

  • Genotype, phenotype

Step-by-Step Guidance

  1. Define mutation in the context of genetics.

  2. Explain how mutations can affect genotype and phenotype.

Try solving on your own before revealing the answer!

Q14. List and describe several types of mutations (point, frameshift, nonsense, missense).

Background

Topic: Types of Mutations

This question asks you to identify and explain different kinds of genetic mutations.

Key Terms:

  • Point mutation: Change in a single nucleotide

  • Frameshift mutation: Insertion or deletion that shifts the reading frame

  • Nonsense mutation: Mutation that introduces a stop codon

  • Missense mutation: Mutation that changes one amino acid

Step-by-Step Guidance

  1. Define each type of mutation listed.

  2. Give an example or describe the effect of each mutation on the protein product.

Try solving on your own before revealing the answer!

Q15. Explain the operon model of transcriptional control in prokaryotes.

Background

Topic: Gene Regulation in Prokaryotes

This question is about how groups of genes are regulated together in bacteria.

Key Terms:

  • Operon: Cluster of genes under control of a single promoter

  • Promoter, operator, repressor, structural genes

Step-by-Step Guidance

  1. Define what an operon is and its components.

  2. Describe how the operon model allows coordinated regulation of gene expression.

  3. Give an example (e.g., lac operon) and explain how it works.

Try solving on your own before revealing the answer!

Q16. What is the difference between vertical and horizontal gene transfer?

Background

Topic: Gene Transfer Mechanisms

This question is about how genetic material is passed on in bacteria and other organisms.

Key Terms:

  • Vertical gene transfer: Parent to offspring

  • Horizontal gene transfer: Between unrelated cells

Step-by-Step Guidance

  1. Define vertical gene transfer and give an example.

  2. Define horizontal gene transfer and give an example.

  3. Explain why horizontal gene transfer is important in microbial evolution.

Try solving on your own before revealing the answer!

Q17. Compare the following mechanisms of genetic recombination in bacteria: transformation, conjugation, and transduction.

Background

Topic: Bacterial Genetic Recombination

This question is about the different ways bacteria can exchange genetic material.

Key Terms:

  • Transformation: Uptake of naked DNA

  • Conjugation: Direct transfer via pilus

  • Transduction: Transfer by bacteriophage

Step-by-Step Guidance

  1. Define each mechanism of genetic recombination.

  2. Describe the process and requirements for each mechanism.

  3. Compare the advantages and limitations of each method.

Try solving on your own before revealing the answer!

Q18. Define genetics, genome, chromosome, plasmid, gene, intron, exon, pili, bacteriophage (phage), genotype, and phenotype.

Background

Topic: Key Genetic Terms

This question is about understanding and defining important vocabulary in microbial genetics.

Key Terms:

  • Genetics: Study of heredity

  • Genome: All genetic material

  • Chromosome: DNA molecule with part/all genetic material

  • Plasmid: Small, circular DNA in bacteria

  • Gene: Segment of DNA coding for a product

  • Intron: Non-coding sequence

  • Exon: Coding sequence

  • Pili: Appendages for attachment or DNA transfer

  • Bacteriophage: Virus that infects bacteria

  • Genotype: Genetic makeup

  • Phenotype: Observable traits

Step-by-Step Guidance

  1. Write a concise definition for each term.

  2. Provide an example or context for each term where possible.

Try solving on your own before revealing the answer!

Q19. Define the following key terms related to microbial control: sterilization, disinfection, antisepsis, degerming, sanitization, pasteurization, “-cide”, and “-stat”.

Background

Topic: Microbial Control Terminology

This question is about understanding the vocabulary used to describe methods of controlling microbial growth.

Key Terms:

  • Sterilization: Removal of all microbes

  • Disinfection: Removal of most pathogens

  • Antisepsis: Disinfection of living tissue

  • Degerming: Removal by mechanical means

  • Sanitization: Lowering microbial counts to safe levels

  • Pasteurization: Heat treatment to reduce microbes

  • -cide: Suffix meaning to kill

  • -stat: Suffix meaning to inhibit growth

Step-by-Step Guidance

  1. Define each term clearly.

  2. Give an example of when each method or term would be used.

Try solving on your own before revealing the answer!

Q20. Describe how antimicrobial agents act against cell walls, cytoplasmic membrane, proteins, and nucleic acids.

Background

Topic: Mechanisms of Antimicrobial Action

This question is about how different agents kill or inhibit microbes by targeting specific cellular structures.

Key Terms:

  • Cell wall disruption

  • Membrane damage

  • Protein denaturation

  • Nucleic acid damage

Step-by-Step Guidance

  1. List the main cellular targets of antimicrobial agents.

  2. Describe how agents disrupt each target (e.g., lysozyme breaks cell wall, alcohol disrupts membranes).

  3. Explain the consequences for the microbe when each target is damaged.

Try solving on your own before revealing the answer!

Q21. List, compare, and contrast specific uses of the following physical methods: heat (moist heat, boiling, steam, autoclaving, pasteurization), dry heat (direct flaming, incineration, hot air), cold, desiccation, and radiation (ionizing and nonionizing), osmotic pressure.

Background

Topic: Physical Methods of Microbial Control

This question is about the different physical methods used to control microbial growth and their applications.

Key Terms:

  • Moist heat vs. dry heat

  • Radiation types

  • Osmotic pressure

Step-by-Step Guidance

  1. List each physical method and describe how it works to control microbes.

  2. Compare the effectiveness and uses of each method.

  3. Contrast the advantages and disadvantages of each method.

Try solving on your own before revealing the answer!

Q22. List, compare, and contrast specific uses of the following chemical disinfectants: phenol, phenolics, halogens (iodine, iodophors, chlorine), alcohols, soap, and ethylene oxide.

Background

Topic: Chemical Methods of Microbial Control

This question is about the different chemicals used to disinfect and their specific applications.

Key Terms:

  • Phenol, phenolics

  • Halogens

  • Alcohols

  • Soaps

  • Ethylene oxide

Step-by-Step Guidance

  1. List each chemical disinfectant and describe its mechanism of action.

  2. Compare their effectiveness and typical uses.

  3. Contrast their advantages and disadvantages.

Try solving on your own before revealing the answer!

Q23. List factors to consider in selecting a microbial control method.

Background

Topic: Choosing Microbial Control Methods

This question is about the considerations that influence the choice of a method to control microbial growth.

Key Terms:

  • Nature of the microbe

  • Environment

  • Material to be treated

  • Safety, cost, effectiveness

Step-by-Step Guidance

  1. List the main factors that influence the choice of a control method.

  2. Explain why each factor is important.

  3. Give examples of how these factors affect the decision.

Try solving on your own before revealing the answer!

Q24. Describe the four BSL’s levels and give examples of each.

Background

Topic: Biosafety Levels

This question is about the classification of laboratory safety levels and the types of organisms handled at each level.

Key Terms:

  • BSL-1: Basic, non-pathogenic microbes

  • BSL-2: Moderate risk, e.g., Staphylococcus aureus

  • BSL-3: High risk, airborne pathogens

  • BSL-4: Extreme risk, dangerous/exotic pathogens

Step-by-Step Guidance

  1. Define each biosafety level and the precautions required.

  2. Give an example organism or situation for each level.

  3. Explain why increasing levels require more stringent controls.

Try solving on your own before revealing the answer!

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