Genetic Engineering & Biotechnology — Hard Practice Quiz

A Biology cheat sheet for Genetic Engineering & Biotechnology — every key formula with its symbols defined — plus a hard-level practice quiz to test recall.

Practice quiz

1. A scientist aims to create a transgenic bacterium capable of producing a human protein. They first isolate the human gene, then use restriction enzymes to cut both the human DNA and a bacterial plasmid. After ligation, the recombinant plasmid is introduced into bacteria. To confirm successful insertion and orientation, they perform PCR on the bacterial colonies, followed by gel electrophoresis of the PCR products. If the human gene contains an internal restriction site for the enzyme used, and the primers for PCR flank this entire gene, what would be the expected outcome on the gel electrophoresis if the gene was successfully inserted and amplified, compared to a scenario where the gene was inserted but a mutation occurred, eliminating the internal restriction site?

   • In the first scenario, two smaller fragments would be observed, while in the second, a single larger fragment would be observed.
   • In the first scenario, a single larger fragment would be observed, while in the second, two smaller fragments would be observed.
   • In both scenarios, a single fragment of the same size would be observed, as PCR amplifies the entire region.
   • In the first scenario, no fragments would be observed due to digestion, while in the second, a single fragment would be observed.

   Answer: In the first scenario, two smaller fragments would be observed, while in the second, a single larger fragment would be observed.

2. A plant breeder wants to develop a new variety of fruit that is both resistant to a common fungal disease and produces significantly larger fruits. They start by crossing two existing varieties, one known for disease resistance and the other for large fruit size. After several generations, they select the best offspring. To further enhance fruit size and potentially introduce novel traits, they then treat the selected plants with a chemical that prevents meiotic separation. Which combination of techniques is being employed, and what are the potential outcomes and risks?

   • Hybridization followed by induced polyploidy; results in larger, stronger plants but can lead to sterility.
   • Inbreeding followed by induced mutations; results in increased homozygosity and potentially new traits, but also genetic defects.
   • Reproductive cloning followed by genetic engineering; results in genetically identical organisms with modified traits, but is complex and costly.
   • Reverse genetics followed by selective breeding; results in understanding gene function and then selecting desired traits, but is not focused on increasing chromosome sets.

   Answer: Hybridization followed by induced polyploidy; results in larger, stronger plants but can lead to sterility.

3. Consider a scenario where a pharmaceutical company is developing a new drug based on a human protein. They decide to produce this protein using molecular cloning in bacteria. After successfully creating recombinant DNA and transforming bacteria, they need to ensure the bacteria are indeed producing the desired human protein. Which of the following approaches would be most effective for verifying the presence and functionality of the *recombinant protein*?

   • Performing gel electrophoresis on bacterial DNA to confirm plasmid size.
   • Using PCR to amplify the inserted human gene from bacterial colonies.
   • Analyzing the bacterial proteome for the specific human protein's signature and activity.
   • Sequencing the entire bacterial genome to confirm gene insertion.

   Answer: Analyzing the bacterial proteome for the specific human protein's signature and activity.

4. A researcher is studying a genetic disorder caused by a single nucleotide polymorphism (SNP) that creates a new restriction enzyme recognition site within a specific gene. They want to develop a diagnostic test using gel electrophoresis. They isolate DNA from a patient, amplify the region containing the SNP using PCR, and then digest the PCR product with the specific restriction enzyme. If the normal allele produces a single $500 \text{ bp}$ fragment and the disease allele, due to the new restriction site, is cut into $300 \text{ bp}$ and $200 \text{ bp}$ fragments, what would be observed on a gel electrophoresis for a heterozygous individual?

   • A single band at $500 \text{ bp}$.
   • Two bands, one at $300 \text{ bp}$ and one at $200 \text{ bp}$.
   • Three bands, one at $500 \text{ bp}$, one at $300 \text{ bp}$, and one at $200 \text{ bp}$.
   • A single band at $250 \text{ bp}$.

   Answer: Three bands, one at $500 \text{ bp}$, one at $300 \text{ bp}$, and one at $200 \text{ bp}$.

5. A new agricultural crop is developed using genetic engineering to incorporate a gene from a bacterium that confers resistance to a specific herbicide. This allows farmers to spray herbicides that kill weeds without harming the crop. However, concerns are raised about the potential for this herbicide resistance gene to transfer to wild relatives of the crop, creating "superweeds." This scenario primarily highlights which two ethical and impact considerations?

   • The benefits of increased yield and the risks of corporate control over seeds.
   • The potential for unknown ecological effects and the ethics of human modification.
   • The advantages of pest resistance and the privacy concerns related to genetic information.
   • The pros and cons of GM foods, specifically concerning environmental impact and gene flow.

   Answer: The pros and cons of GM foods, specifically concerning environmental impact and gene flow.

6. A scientist is attempting to map the relative positions of three genes (A, B, and C) on a chromosome. They perform crosses and observe the following recombination frequencies:\n* Genes A and B: $15\%$\n* Genes B and C: $5\%$\n* Genes A and C: $10\%$\nBased on these frequencies, what is the most likely order of the genes on the chromosome, and what does this method primarily contribute to?

   • Order: A-C-B; contributes to creating a physical map.
   • Order: C-B-A; contributes to understanding gene function through reverse genetics.
   • Order: A-C-B; contributes to creating a genetic map.
   • Order: B-A-C; contributes to whole genome sequencing.

   Answer: Order: A-C-B; contributes to creating a genetic map.

7. A research team is investigating a novel gene in a model organism suspected to be involved in a critical developmental pathway. They decide to use reverse genetics to understand its function. They create a transgenic organism where this specific gene has been intentionally disrupted. Subsequently, they observe a severe developmental defect in the knockout organism. To further characterize the molecular consequences of this gene disruption, which advanced technique would be most appropriate to analyze the overall changes in protein expression patterns in the affected tissues?

   • Whole genome sequencing to identify other mutated genes.
   • Gel electrophoresis to separate DNA fragments by size.
   • Proteomics to study the entire set of expressed proteins.
   • Polymerase Chain Reaction (PCR) to amplify the disrupted gene.

   Answer: Proteomics to study the entire set of expressed proteins.

8. A patient is diagnosed with a rare genetic disorder. Genetic testing reveals a specific mutation. The physician suggests a personalized medicine approach, tailoring drug dosages based on the patient's unique genetic makeup. To achieve this, the patient undergoes a comprehensive analysis of their entire genetic code. Which advanced genomics technique is primarily being utilized, and what field of study does this personalized drug response fall under?

   • Metagenomics and genetic mapping.
   • Whole genome sequencing and pharmacogenomics.
   • Molecular cloning and proteomics.
   • Reverse genetics and gene therapy.

   Answer: Whole genome sequencing and pharmacogenomics.

9. A scientist is developing a new variety of banana that is resistant to a devastating fungal blight. They successfully create a plant with three sets of chromosomes ($3N$) using a chemical treatment. This new variety exhibits increased vigor and larger fruits compared to its diploid ancestors. However, attempts to cross this $3N$ banana with a normal $2N$ banana result in sterile offspring. What is the primary technique used to create the $3N$ banana, and why might the offspring of the $3N \times 2N$ cross be sterile?

   • Induced mutation; sterility due to incompatible gene sequences.
   • Polyploidy; sterility due to uneven chromosome segregation during meiosis.
   • Hybridization; sterility due to genetic defects from inbreeding.
   • Reproductive cloning; sterility due to lack of genetic variation.

   Answer: Polyploidy; sterility due to uneven chromosome segregation during meiosis.

10. CRISPR-Cas9 technology has revolutionized gene editing, allowing for precise modifications to DNA sequences. If a researcher uses CRISPR-Cas9 to correct a specific point mutation responsible for a genetic disease in human somatic cells, what is the primary goal of this intervention, and what ethical consideration is directly addressed by focusing on somatic cells rather than germline cells?

    • The primary goal is reproductive cloning; it addresses concerns about patenting human DNA.
    • The primary goal is gene therapy; it avoids the ethical concerns associated with heritable changes to the human genome.
    • The primary goal is to create transgenic organisms; it addresses concerns about genetic discrimination (GINA).
    • The primary goal is to increase genetic variation; it avoids the ethical concerns of corporate control over GM foods.

    Answer: The primary goal is gene therapy; it avoids the ethical concerns associated with heritable changes to the human genome.