MCB3020 Final Exam Study Guide – Microbiology Concepts and Practice Questions

Q1. What was the first widely used method for DNA sequencing and how does it work?

Background

Topic: Microbial Genomics – DNA Sequencing Methods

This question tests your understanding of the history and mechanism of DNA sequencing, a foundational technique in genomics.

Key Terms and Concepts:

• DNA sequencing: Determining the order of nucleotides in DNA.

• Sanger sequencing: The first widely used method for sequencing DNA.

• Dideoxynucleotides (ddNTPs): Modified nucleotides used to terminate DNA synthesis in Sanger sequencing.

Step-by-Step Guidance

1. Recall the name of the first widely adopted DNA sequencing method.

2. Think about the main principle behind this method—what special nucleotides are used to terminate DNA synthesis?

3. Consider how the incorporation of these nucleotides allows for the determination of DNA sequence.

4. Reflect on how the resulting DNA fragments are separated and analyzed to read the sequence.

Try solving on your own before revealing the answer!

Final Answer:

The first widely used method for DNA sequencing was Sanger sequencing (also known as the chain-termination method). It works by using dideoxynucleotides (ddNTPs) to terminate DNA strand elongation during replication. By incorporating these chain-terminating nucleotides, DNA fragments of varying lengths are produced, each ending at a specific nucleotide. These fragments are then separated by size using gel electrophoresis, and the DNA sequence is determined by reading the order of the terminated fragments.

Q2. What additional sequencing methods are available and how do they compare to the above method with regard to cost and throughput?

Background

Topic: Advances in DNA Sequencing Technologies

This question focuses on comparing newer sequencing technologies to Sanger sequencing, especially in terms of efficiency and cost.

Key Terms and Concepts:

• Next-generation sequencing (NGS): High-throughput sequencing technologies.

• Throughput: The amount of data generated per run.

• Cost per base: The expense of sequencing each nucleotide.

Step-by-Step Guidance

1. List at least two modern sequencing methods that have been developed after Sanger sequencing.

2. Consider how these methods differ in the number of DNA fragments they can sequence simultaneously (throughput).

3. Think about how the cost per base compares between Sanger sequencing and these newer methods.

4. Reflect on the practical implications of these differences for large-scale genomics projects.

Try solving on your own before revealing the answer!

Final Answer:

Additional sequencing methods include next-generation sequencing (NGS) platforms such as Illumina (sequencing by synthesis), 454 pyrosequencing, and Ion Torrent, as well as third-generation methods like PacBio and Oxford Nanopore. Compared to Sanger sequencing, these methods offer much higher throughput (millions to billions of sequences per run) and significantly lower cost per base, making them more suitable for large-scale projects like whole-genome sequencing.

Q3. What is genome annotation?

Background

Topic: Genomics – Genome Analysis

This question tests your understanding of the process of identifying functional elements within a sequenced genome.

Key Terms and Concepts:

• Genome annotation: The process of identifying genes and other functional elements in a DNA sequence.

• Open reading frame (ORF): A sequence of DNA that could potentially encode a protein.

Step-by-Step Guidance

1. Define what is meant by genome annotation in the context of genomics.

2. Think about the main steps involved in annotating a genome after sequencing.

3. Consider what types of features are identified during annotation (e.g., genes, regulatory elements).

Try solving on your own before revealing the answer!

Final Answer:

Genome annotation is the process of identifying and labeling the locations of genes and other functional elements (such as regulatory sequences, tRNAs, and rRNAs) within a sequenced genome. This involves predicting open reading frames (ORFs) and assigning potential functions based on sequence similarity to known genes.

Q4. How does a metagenome differ from a genome?

Background

Topic: Metagenomics vs. Genomics

This question examines your understanding of the difference between sequencing the DNA of a single organism versus a community of organisms.

Key Terms and Concepts:

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

• Metagenome: The collective genetic material from all organisms in an environmental sample.

Step-by-Step Guidance

1. Define what is meant by a genome in microbiology.

2. Define what is meant by a metagenome.

3. Compare the two in terms of the source and complexity of the DNA being analyzed.

Try solving on your own before revealing the answer!

Final Answer:

A genome refers to the complete DNA sequence of a single organism, while a metagenome is the combined genetic material from all organisms present in an environmental sample. Metagenomics allows for the study of microbial communities without the need to culture individual species.

Q5. Which eukaryotic organelles have their own genomes?

Background

Topic: Organelle Genomes

This question tests your knowledge of endosymbiotic theory and the genetic autonomy of certain organelles.

Key Terms and Concepts:

• Mitochondria: Energy-producing organelles with their own DNA.

• Chloroplasts: Photosynthetic organelles with their own DNA.

Step-by-Step Guidance

1. Recall which organelles in eukaryotic cells are believed to have originated from endosymbiotic events.

2. Think about which organelles contain their own circular DNA, separate from the nuclear genome.

Try solving on your own before revealing the answer!

Final Answer:

Mitochondria and chloroplasts are the two eukaryotic organelles that have their own genomes. This supports the endosymbiotic theory, which proposes that these organelles originated from free-living bacteria.

Q6. How do proteomes and transcriptomes differ?

Background

Topic: Omics – Proteomics vs. Transcriptomics

This question focuses on the difference between the study of all proteins and all RNA transcripts in a cell or organism.

Key Terms and Concepts:

• Proteome: The entire set of proteins expressed by a genome, cell, tissue, or organism.

• Transcriptome: The complete set of RNA transcripts produced by the genome.

Step-by-Step Guidance

1. Define what is meant by the proteome and the transcriptome.

2. Consider the relationship between gene expression (transcription) and protein production (translation).

3. Think about how the proteome and transcriptome can differ in content and function.

Try solving on your own before revealing the answer!

Final Answer:

The transcriptome includes all RNA molecules transcribed from the genome, while the proteome consists of all proteins translated from those RNAs. The proteome reflects the functional molecules in the cell, and its composition can differ from the transcriptome due to post-transcriptional and post-translational regulation.

Q7. Which ‘omics provide information about potential activity, gene expression, or activity of communities and single cells?

Background

Topic: Functional Omics

This question asks you to connect different 'omics' approaches to the type of biological information they reveal.

Key Terms and Concepts:

• Genomics: Study of DNA sequences.

• Transcriptomics: Study of RNA expression.

• Proteomics: Study of protein expression.

• Metabolomics: Study of small-molecule metabolites.

Step-by-Step Guidance

1. List the main 'omics' fields and what each measures.

2. Identify which 'omics' approaches provide information about gene expression and cellular activity.

3. Consider how these approaches can be applied to both communities and single cells.

Try solving on your own before revealing the answer!

Final Answer:

Transcriptomics (RNA-seq) provides information about gene expression, proteomics reveals protein activity, and metabolomics shows metabolic activity. These approaches can be used to study both microbial communities and single cells, giving insight into potential and actual biological activity.