Question 1

A forensic scientist finds that 30% of the bases in a DNA sample are adenine (A). Using base-pairing rules, what percentage of the DNA bases should be cytosine (C)?

Accepted Answer

20%

Question 2

A pharmaceutical company develops a drug that prevents mRNA from being translated into proteins in bacteria. Which part of the central dogma does this drug target, and what effect would it have on bacterial survival?

Accepted Answer

Translation; it would prevent protein synthesis and likely kill the bacteria.

Question 3

A hospital is treating a patient infected with antibiotic-resistant bacteria. Scientists develop a new drug that prevents DNA polymerase from functioning. How would this impact bacterial replication, and could this be an effective treatment?

Accepted Answer

It would block DNA replication, preventing bacterial cell division and could be an effective treatment.

Question 4

A geneticist is studying a rare bacterial mutation that causes Okazaki fragments to form incorrectly. What effect would this mutation have on DNA replication, and why would it only affect the lagging strand?

Accepted Answer

It would disrupt synthesis of the lagging strand because Okazaki fragments are only formed there.

Question 5

Doctors use a drug to treat tuberculosis that specifically blocks RNA polymerase in bacterial cells. How does this prevent bacterial growth, and why doesn’t it affect human cells in the same way?

Accepted Answer

Bacterial RNA polymerase is structurally different from human RNA polymerase, so the drug selectively inhibits bacterial transcription.

Question 6

A patient with a bacterial infection is prescribed an antibiotic that binds to bacterial ribosomes, preventing mRNA from attaching. How will this antibiotic stop bacterial growth, and why won’t it affect human ribosomes?

Accepted Answer

Bacterial ribosomes are structurally different (70S vs. 80S), so the antibiotic selectively inhibits bacterial protein synthesis.

Question 7

A scientist provides the DNA coding strand sequence 5'-ATG GGC TTT TAA-3'. What is the corresponding mRNA sequence, and how does this process relate to biotechnology applications such as insulin production?

Accepted Answer

5'-AUG GGC UUU UAA-3'; mRNA is transcribed from DNA and used to produce proteins like insulin in biotechnology.

Question 8

Explain how the locations of transcription and translation differ between prokaryotic and eukaryotic cells, and why this difference is important for understanding how antibiotics or genetic diseases affect human health.

Accepted Answer

In prokaryotes, transcription and translation occur simultaneously in the cytoplasm; in eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm. This affects antibiotic targeting and genetic disease expression.

Question 9

A hospital discovers a bacterial strain that has developed resistance to an antibiotic after a single nucleotide change in its DNA. What type of mutation most likely occurred, and how could this affect the protein produced?

Accepted Answer

A point mutation; it could change a single amino acid, potentially altering the protein’s function.

Question 10

A research lab is studying a bacterial mutation where one nucleotide is deleted from a gene, shifting the entire reading frame. How would this affect the resulting protein, and why would it likely cause more damage than a point mutation?

Accepted Answer

It causes a frameshift mutation, altering every amino acid downstream and likely producing a nonfunctional protein.

Question 11

Doctors are investigating an outbreak of antibiotic-resistant bacteria in a hospital. Genetic tests show that the resistance genes are located on plasmids. Was this resistance most likely acquired through conjugation or transformation, and how does this affect the spread of resistance?

Accepted Answer

Conjugation; plasmids can be transferred directly between bacteria, rapidly spreading resistance.

Question 12

A scientist is studying how bacteria rapidly build proteins and DNA during an infection. What type of metabolic pathway are they using, and why do these anabolic reactions require energy input?

Accepted Answer

Anabolic pathways; they require energy input because building complex molecules from simpler ones is energetically unfavorable ($$\Delta G \u003e 0).$$

Question 13

A detergent company is using heat-resistant bacterial enzymes in its products to break down proteins and fats. How do these enzymes lower activation energy, and why are they beneficial for high-temperature cleaning?

Accepted Answer

Enzymes lower activation energy ($$E_a) by $$stabilizing the transition state, allowing reactions to occur faster even at high temperatures.

Question 14

A microbiologist is studying two bacterial strains: one that thrives in oxygen-rich environments and another that survives without oxygen. What differences in cellular respiration would you expect between these two bacteria, and which one would produce more ATP per glucose molecule?

Accepted Answer

The aerobic bacterium uses oxidative phosphorylation and produces more ATP ($$\approx 36$$ ATP/glucose) than the anaerobic bacterium ($$\approx 2$$ ATP/glucose).

Question 15

A researcher is studying a bacterial species that cannot convert pyruvate into Acetyl-CoA. How will this affect the citric acid cycle, and what alternative pathways might the bacteria use to generate energy?

Accepted Answer

The citric acid cycle will be blocked; bacteria may use fermentation to generate ATP.

Question 16

A pharmaceutical company develops a drug that prevents protons from being pumped across the bacterial inner membrane. How would this affect the electron transport chain, and why would it reduce ATP production in bacteria?

Accepted Answer

It would disrupt the proton gradient ($$\Delta pH$$), preventing ATP synthase from generating ATP via chemiosmosis.

Question 17

A scientist is studying the citric acid cycle and metabolism. Which alternative pathways might bacteria use to generate ATP if the citric acid cycle is blocked, and what cannot convert pyruvate into Acetyl-CoA?

Accepted Answer

Fermentation; bacteria can convert pyruvate to lactate or ethanol to generate ATP anaerobically.

Question 18

Label the major steps of the image below (DNA replication) and identify where most ATP is made. Be able to pick out the major steps and describe them (overview).

Accepted Answer

Most ATP is made during oxidative phosphorylation in the electron transport chain; major steps in DNA replication include unwinding by helicase, synthesis by DNA polymerase, and joining of Okazaki fragments by ligase.

Microbiology Exam 2 Review: DNA, Genetics, and Bacterial Metabolism

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