Final Exam Study Guide: Molecular Genetics, Gene Expression, and Biotechnology

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Q1. What is gene expression? What are the two phases involved?

Background

Topic: Gene Expression

This question tests your understanding of how genetic information in DNA is used to direct the synthesis of proteins, a fundamental concept in molecular biology.

Key Terms:

Gene Expression: The process by which information from a gene is used to synthesize a functional gene product (often a protein).
Transcription: The synthesis of RNA from a DNA template.
Translation: The synthesis of a protein using the information in mRNA.

Step-by-Step Guidance

Recall that gene expression involves two main stages: transcription and translation.
Think about where each process occurs in a eukaryotic cell (nucleus vs. cytoplasm).
Consider what each stage accomplishes: transcription produces mRNA, and translation produces a polypeptide.

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Q2. Describe the processes of transcription and translation in detail (initiation, elongation, and termination), including where each one takes place.

Background

Topic: Transcription and Translation Mechanisms

This question assesses your knowledge of the steps involved in gene expression, focusing on the molecular events during transcription and translation.

Key Terms:

Initiation: The beginning of transcription or translation, involving assembly of necessary components.
Elongation: The process of adding nucleotides (transcription) or amino acids (translation) to the growing chain.
Termination: The end of the process, where the newly made RNA or protein is released.

Step-by-Step Guidance

For transcription, identify the three main stages: initiation, elongation, and termination. Consider what happens at each stage and which enzymes are involved.
For translation, also break down the process into initiation, elongation, and termination. Think about the roles of ribosomes, tRNA, and mRNA.
Note the cellular locations: transcription occurs in the nucleus (in eukaryotes), while translation occurs in the cytoplasm.
Summarize the key events in each stage for both processes.

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Q3. What is the central dogma and how do you transcribe and translate a given DNA sequence?

Background

Topic: Central Dogma of Molecular Biology

This question tests your understanding of the flow of genetic information from DNA to RNA to protein, and your ability to apply this to a sequence.

Key Terms and Formulas:

Central Dogma: DNA → RNA → Protein
Transcription: DNA is used as a template to make mRNA.
Translation: mRNA is used as a template to assemble amino acids into a polypeptide.
Codon: A sequence of three mRNA nucleotides that codes for a specific amino acid.

Step-by-Step Guidance

Given a DNA sequence, write the complementary mRNA sequence by replacing A with U, T with A, C with G, and G with C.
Divide the mRNA sequence into codons (groups of three nucleotides).
Use a genetic code table to determine which amino acid each codon specifies.

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Q4. Explain the operon model of gene regulation in bacteria. How do the lac operon and trp operon work? What are repressors and inducers? Distinguish between inducible and repressible operons.

Background

Topic: Gene Regulation in Prokaryotes

This question focuses on how bacteria control gene expression using operons, and the differences between types of operons.

Key Terms:

Operon: A cluster of genes under the control of a single promoter and operator.
Repressor: A protein that binds to the operator to block transcription.
Inducer: A molecule that inactivates the repressor and allows transcription.
Inducible Operon: Usually off; can be turned on by an inducer (e.g., lac operon).
Repressible Operon: Usually on; can be turned off by a corepressor (e.g., trp operon).

Step-by-Step Guidance

Describe the basic structure of an operon (promoter, operator, structural genes).
Explain how the lac operon is regulated by the presence or absence of lactose (inducible system).
Explain how the trp operon is regulated by the presence or absence of tryptophan (repressible system).
Define the roles of repressors and inducers in these systems.
Summarize the difference between inducible and repressible operons.

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Q5. Describe the process of making recombinant DNA using restriction enzymes, plasmids, and ligase. How is recombinant DNA inserted into bacteria?

Background

Topic: Recombinant DNA Technology

This question tests your understanding of the steps involved in creating recombinant DNA molecules and introducing them into bacterial cells.

Key Terms:

Restriction Enzymes: Enzymes that cut DNA at specific sequences.
Plasmids: Small, circular DNA molecules used as vectors.
Ligase: Enzyme that joins DNA fragments together.
Transformation: The process of introducing recombinant DNA into bacteria.

Step-by-Step Guidance

Identify the gene of interest and cut both the gene and plasmid with the same restriction enzyme to create compatible ends.
Mix the cut gene and plasmid together; use DNA ligase to seal the fragments, forming recombinant DNA.
Introduce the recombinant plasmid into bacteria through transformation.

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Q6. What is the polymerase chain reaction (PCR) and what are its main steps?

Background

Topic: DNA Amplification

This question tests your understanding of PCR, a technique used to amplify DNA sequences.

Key Terms:

PCR: Polymerase Chain Reaction, a method to make many copies of a DNA segment.
Taq Polymerase: A heat-stable DNA polymerase used in PCR.
Denaturation, Annealing, Extension: The three main steps of PCR.

Step-by-Step Guidance

Describe the denaturation step: heating the DNA to separate strands.
Explain the annealing step: cooling to allow primers to bind to target sequences.
Describe the extension step: Taq polymerase synthesizes new DNA strands.
Note that these steps are repeated for many cycles to amplify the DNA.

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Q7. Describe the general structure of a virus and the steps of viral infection. Explain the lytic and lysogenic cycles, distinguish between virulent and temperate phages, and define prions. Why are viruses considered non-living?

Background

Topic: Viruses and Viral Life Cycles

This question covers the structure of viruses, their replication cycles, and the nature of prions.

Key Terms:

Capsid: Protein coat surrounding viral genetic material.
Lytic Cycle: Viral replication that destroys the host cell.
Lysogenic Cycle: Viral DNA integrates into host genome and replicates with it.
Virulent Phage: Only undergoes lytic cycle.
Temperate Phage: Can undergo both lytic and lysogenic cycles.
Prion: Infectious protein particles.

Step-by-Step Guidance

Describe the basic structure of a virus (genetic material, capsid, sometimes envelope).
Outline the steps of viral infection: attachment, entry, replication, assembly, release.
Compare the lytic and lysogenic cycles, and define virulent vs. temperate phages.
Explain what prions are and why viruses are not considered living organisms.

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Q8. Describe the HIV infection cycle. Why is HIV called a retrovirus? How are retroviruses different from other viruses?

Background

Topic: Retroviruses and HIV

This question tests your understanding of the unique features of retroviruses and the HIV life cycle.

Key Terms:

Retrovirus: A virus that uses reverse transcriptase to convert its RNA genome into DNA.
Reverse Transcriptase: Enzyme that synthesizes DNA from an RNA template.
HIV: Human Immunodeficiency Virus, a retrovirus that infects immune cells.

Step-by-Step Guidance

Outline the steps of HIV infection: entry, reverse transcription, integration, transcription, translation, assembly, and release.
Explain why HIV is classified as a retrovirus (use of reverse transcriptase).
Compare retroviruses to other viruses in terms of their replication strategies.

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Q9. What is the role of oncogenes and tumor suppressor genes in the development of cancer?

Background

Topic: Cancer Genetics

This question focuses on the genetic basis of cancer, specifically the roles of genes that promote or inhibit cell division.

Key Terms:

Oncogene: A mutated gene that promotes uncontrolled cell division.
Tumor Suppressor Gene: A gene that normally inhibits cell division or causes apoptosis.

Step-by-Step Guidance

Define oncogenes and explain how mutations can convert proto-oncogenes into oncogenes.
Describe the normal function of tumor suppressor genes and what happens when they are inactivated.
Explain how the balance between these genes affects cell cycle regulation and cancer development.

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Q10. What is the role of miRNA in gene regulation?

Background

Topic: Noncoding RNA and Gene Regulation

This question tests your understanding of how small RNA molecules can regulate gene expression post-transcriptionally.

Key Terms:

miRNA (microRNA): Small noncoding RNA molecules that bind to mRNA to inhibit translation or promote degradation.

Step-by-Step Guidance

Define miRNA and describe how it is produced in the cell.
Explain how miRNA binds to target mRNA molecules.
Describe the effects of miRNA binding on gene expression (translation inhibition or mRNA degradation).

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Q11. How does RNA differ from DNA? What is a codon and what is its relationship to an anticodon? How do you transcribe DNA into mRNA and translate it into a polypeptide?

Background

Topic: Nucleic Acids and the Genetic Code

This question covers the structural differences between DNA and RNA, and the mechanics of transcription and translation.

Key Terms:

DNA vs. RNA: DNA contains deoxyribose, is double-stranded, and uses thymine; RNA contains ribose, is single-stranded, and uses uracil.
Codon: Three-nucleotide sequence on mRNA that codes for an amino acid.
Anticodon: Three-nucleotide sequence on tRNA complementary to the mRNA codon.

Step-by-Step Guidance

List the main structural differences between DNA and RNA.
Define codon and anticodon, and explain their roles in translation.
Given a DNA sequence, write the corresponding mRNA sequence (transcription).
Divide the mRNA into codons and use the genetic code to determine the amino acid sequence (translation).

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Q12. Define and explain the functions of: operon, promoter, operator, repressor, corepressor, inducible operon, repressible operon. How do the trp and lac operons work? What is the role of differential gene expression and noncoding RNA in gene regulation?

Background

Topic: Prokaryotic and Eukaryotic Gene Regulation

This question tests your understanding of gene regulation mechanisms in both prokaryotes and eukaryotes.

Key Terms:

Operon: Cluster of genes under a single promoter.
Promoter: DNA sequence where RNA polymerase binds to start transcription.
Operator: DNA segment where a repressor can bind.
Repressor: Protein that inhibits gene transcription.
Corepressor: Molecule that activates a repressor protein.
Inducible/Repressible Operon: Systems that can be turned on/off by inducers or corepressors.
Differential Gene Expression: Expression of different genes by cells with the same genome.
Noncoding RNA: RNA molecules (e.g., miRNA, siRNA) that regulate gene expression.

Step-by-Step Guidance

Define each term and describe its role in gene regulation.
Explain how the trp operon (repressible) and lac operon (inducible) function in bacteria.
Discuss the importance of differential gene expression in multicellular organisms.
Describe how noncoding RNAs can regulate gene expression.

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Q13. Describe the role of plasmids, restriction endonucleases, and ligase in molecular cloning. Define cDNA and the role of reverse transcriptase. What is the purpose of PCR? What are transgenic organisms and their impact?

Background

Topic: Biotechnology and Genetic Engineering

This question covers the tools and techniques used in molecular cloning and genetic engineering.

Key Terms:

Plasmid: Circular DNA vector used in cloning.
Restriction Endonuclease: Enzyme that cuts DNA at specific sites.
Ligase: Enzyme that joins DNA fragments.
cDNA: Complementary DNA synthesized from mRNA by reverse transcriptase.
Reverse Transcriptase: Enzyme that synthesizes DNA from an RNA template.
PCR: Technique to amplify DNA.
Transgenic Organism: Organism with foreign DNA inserted into its genome.

Step-by-Step Guidance

Describe how plasmids, restriction enzymes, and ligase are used to clone genes.
Define cDNA and explain how reverse transcriptase is used to make it from mRNA.
State the main purpose of PCR in molecular biology.
Define transgenic organisms and discuss their potential impacts on humans and society.