Question 1

Which of the following best explains why anthrax spores are particularly dangerous as a biological weapon?

Accepted Answer

They can survive for decades in harsh environments and are resistant to heat, desiccation, and many disinfectants.

Question 2

Ciprofloxacin is an antibiotic that targets DNA gyrase and topoisomerase IV in Bacillus anthracis. What is the primary effect of inhibiting these enzymes?

Accepted Answer

It halts DNA replication, preventing bacterial growth.

Question 3

Which of the following best describes the structure of DNA?

Accepted Answer

A double helix composed of a sugar-phosphate backbone and nitrogenous bases.

Question 4

Why are the ends of linear chromosomes (telomeres) more vulnerable to shortening during DNA replication?

Accepted Answer

DNA polymerase cannot fully replicate the 3' ends of linear DNA, leading to progressive shortening.

Question 5

Which types of cells normally have active telomerase?

Accepted Answer

Germ cells, stem cells, and cancer cells.

Question 6

A patient is treated with ciprofloxacin for anthrax exposure. Which molecular process is directly inhibited by this drug?

Accepted Answer

Supercoiling and unwinding of bacterial DNA during replication.

Question 7

If a PCR reaction starts with 1 copy of DNA and is run for 20 cycles, how many copies of DNA will be present after 20 cycles? (Assume 100% efficiency per cycle.)

Accepted Answer

$2^{20}$

Question 8

A restriction enzyme recognizes the sequence CCTGAGG. If a mutation changes this sequence to CCTGTGG, what will happen when the enzyme is added to the DNA?

Accepted Answer

The enzyme will not cut at the mutated site because the recognition sequence is altered.

Question 9

Why do most somatic (body) cells lack telomerase activity, and how does this limit their lifespan?

Accepted Answer

Without telomerase, telomeres shorten with each division, eventually leading to cell senescence.

Question 10

In a DNA fingerprinting experiment, a child inherits one allele from each parent. If the mother has alleles of 220 bp and 600 bp, and the father has alleles of 400 bp and 750 bp, which of the following could be a possible genotype for the child?

Accepted Answer

220 bp and 400 bp

Question 11

Which of the following is a major ethical concern regarding the use of anti-aging treatments that activate telomerase?

Accepted Answer

Potential for increased cancer risk due to uncontrolled cell growth.

Question 12

If a public health official is deciding whether to give antibiotics to thousands of healthy people after an anthrax attack, which of the following is a key risk to consider?

Accepted Answer

Development of antibiotic-resistant bacteria in the population.

Question 13

Which of the following best describes the function of telomerase?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes, preventing telomere shortening.

Question 14

A sickle cell mutation changes the DNA sequence recognized by the restriction enzyme Mst II. What is the consequence of this mutation for restriction digest analysis?

Accepted Answer

The enzyme cannot cut at the mutated site, resulting in a different fragment pattern.

Question 15

Which of the following is a key difference between bacterial and human DNA replication that is exploited by antibiotics like ciprofloxacin?

Accepted Answer

Bacterial DNA replication relies on unique enzymes (e.g., DNA gyrase) not found in humans.

Question 16

A PCR primer is designed to amplify a specific region of chromosome 11. Why is it important that the primer binds only to the target region and not elsewhere in the genome?

Accepted Answer

Non-specific binding would result in amplification of unintended DNA regions, complicating analysis.

Question 17

In a gel electrophoresis experiment, DNA fragments of 800 bp, 400 bp, and 150 bp are loaded into a gel. Which fragment will migrate the farthest from the well?

Accepted Answer

150 bp

Question 18

Which of the following scenarios best illustrates a social risk of distributing antibiotics widely after a bioterrorism event?

Accepted Answer

Unequal access to antibiotics, leading to health disparities among different populations.

Question 19

A 62-year-old woman volunteers for a clinical trial of a drug that activates telomerase in her somatic cells. What is a potential benefit and risk of this therapy?

Accepted Answer

Benefit: slowed aging; Risk: increased cancer risk due to uncontrolled cell growth.

DNA Structure, Replication, Telomerase, and Medical Applications: Study Notes

Study Guide - Practice Questions

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