Q: If you perform 20 cycles of PCR, and each cycle doubles the amount of DNA, how many copies will you have after 20 cycles, starting from a single DNA molecule? Use the formula $$N = N_0$ \times 2^n$$ where $$N_0 is $$the initial number of molecules and $$n is $$the number of cycles.

$$N = 1 \times 2$$^{20}$$ = 1,048,576$$ copies

Question 1

Which of the following best explains why anthrax spores are a significant concern for public health and security?

Accepted Answer

Anthrax spores can survive for decades in harsh environments and resist many disinfectants, making them difficult to eradicate.

Question 2

Which enzyme is targeted by ciprofloxacin to inhibit Bacillus anthracis DNA replication?

Accepted Answer

Topoisomerase IV

Question 3

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

Accepted Answer

DNA polymerase cannot fully replicate the 5' ends of linear DNA, leading to progressive shortening.

Question 4

Which type of cells typically have active telomerase?

Accepted Answer

Germ cells and cancer cells

Question 5

A patient receives a drug that inhibits topoisomerase IV in bacteria. What is the most likely effect on bacterial DNA replication?

Accepted Answer

DNA replication will halt due to inability to relieve supercoiling tension.

Question 6

If you perform 20 cycles of PCR, and each cycle doubles the amount of DNA, how many copies will you have after 20 cycles, starting from a single DNA molecule? Use the formula $$N = N_0$ 	imes 2^n$$ where $$N_0 is $$the initial number of molecules and $$n is $$the number of cycles.

Accepted Answer

$$N = 1 	imes 2$$^{20}$$ = 1,048,576$$ copies

Question 7

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

Accepted Answer

Bacterial DNA replication uses different enzymes, such as DNA gyrase and topoisomerase IV, which are targeted by antibiotics.

Question 8

A restriction enzyme recognizes the sequence CCTGCAGG. If a mutation changes this sequence to CCTGTGGG, what will happen during a restriction digest?

Accepted Answer

The enzyme will not recognize and cut the mutated site, resulting in fewer DNA fragments.

Question 9

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

Accepted Answer

Somatic cells lack telomerase, leading to telomere shortening and eventual cell aging and death.

Question 10

In a gel electrophoresis experiment, DNA fragments of different sizes are loaded into a gel. Which fragment will migrate the farthest from the well?

Accepted Answer

The smallest fragment

Question 11

If a public health official must decide whether to give antibiotics to thousands of healthy people during an anthrax outbreak, which factor should be most carefully considered?

Accepted Answer

The risk of antibiotic resistance developing in the population

Question 12

Which of the following best describes the basic structure of DNA?

Accepted Answer

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

Question 13

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

Accepted Answer

Increased risk of cancer due to uncontrolled cell growth

Question 14

Which of the following is a real-world application of PCR (Polymerase Chain Reaction)?

Accepted Answer

Amplifying specific DNA sequences for genetic testing and disease diagnosis

Question 15

If a child inherits one allele from each parent for a gene, but the alleles are not exactly identical, what is this genetic phenomenon called?

Accepted Answer

Heterozygosity

Question 16

During a restriction digest, if a DNA molecule has two recognition sites for the enzyme, how many fragments will be produced?

Accepted Answer

Three fragments

Question 17

Which of the following is a key ethical consideration when anti-aging treatments become available?

Accepted Answer

Who should have access to the treatment, considering issues of equity and health disparities

Question 18

What is the function of telomerase in cells?

Accepted Answer

Adds repetitive DNA sequences to the ends of chromosomes, preventing telomere shortening

Question 19

Which of the following is a biological risk of distributing antibiotics widely during an anthrax attack?

Accepted Answer

Development of antibiotic-resistant bacteria

Question 20

A DNA sequence is located on chromosome 11. To amplify only that portion using PCR, which component is essential?

Accepted Answer

Primers specific to the target sequence

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

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