Question 1

Which of the following best describes the principle behind DNA sequencing techniques?

Accepted Answer

The principle of complementary base pairing, where each nucleotide added is matched to its complement on the template strand.

Question 2

In the Sanger sequencing method, what is the role of dideoxynucleotides (ddNTPs)?

Accepted Answer

They cause chain termination by lacking a 3'-OH group, resulting in DNA fragments of varying lengths.

Question 3

A researcher wants to amplify a specific DNA sequence from a small sample. Which technique should they use, and what is the key enzyme involved?

Accepted Answer

PCR amplification; Taq polymerase

Question 4

During gel electrophoresis, why do DNA fragments move toward the positive electrode?

Accepted Answer

DNA fragments are negatively charged due to their phosphate backbone and are attracted to the positive electrode.

Question 5

Which equation best represents the release of pyrophosphate (PPi) during DNA sequencing, and what is its significance?

Accepted Answer

$$\mathrm{dNTP} + \mathrm{DNA_{(n)}} \rightarrow \mathrm{DNA_{(n+1)}} + \mathrm{PPi}$$ ; The release of PPi causes a flash of light, indicating nucleotide incorporation.

Question 6

A scientist is creating a recombinant plasmid. Which combination of tools is essential for this process?

Accepted Answer

Restriction enzymes and DNA ligase

Question 7

Why is it challenging to express eukaryotic genes in prokaryotic cells?

Accepted Answer

Eukaryotic genes contain introns and require post-transcriptional modifications that prokaryotes cannot perform.

Question 8

Which of the following best describes the use of DNA microarrays?

Accepted Answer

To measure the expression levels of thousands of genes simultaneously by hybridizing labeled cDNA to probes.

Question 9

In a DNA microarray experiment comparing healthy and cancerous tissue, what does a yellow spot indicate?

Accepted Answer

The gene is expressed in both healthy and cancerous tissue.

Question 10

Which equation represents the conversion of mRNA to cDNA in microarray analysis, and which enzyme is responsible?

Accepted Answer

$$\mathrm{mRNA} \xrightarrow{\mathrm{Reverse\ Transcriptase}} \mathrm{cDNA}$$ ; Reverse transcriptase catalyzes this reaction.

Question 11

Which statement about stem cells is correct?

Accepted Answer

Embryonic stem cells are pluripotent and can differentiate into a variety of specialized cells.

Question 12

A patient with a genetic disorder receives gene therapy using a retroviral vector. What is the main goal of this treatment?

Accepted Answer

To insert a normal allele of the defective gene into the somatic cells of the affected tissue.

Question 13

Which of the following is a practical application of CRISPR-Cas9 gene editing?

Accepted Answer

Altering genes in insects to prevent transmission of diseases like malaria.

Question 14

What is a single nucleotide polymorphism (SNP), and why is it important?

Accepted Answer

A single base pair variation found in at least 1% of the population; it serves as a genetic marker for disease-related alleles.

Question 15

Which equation best represents the exponential amplification of DNA during PCR?

Accepted Answer

$$N = N_0$ 	imes 2^n$$ ; where $$N is $$the number of DNA molecules after $$n$$ cycles.

Question 16

Which of the following is a potential environmental risk associated with genetically modified (GM) crops?

Accepted Answer

Transgenic plants may pass modified genes to close relatives in wild areas, creating 'super weeds'.

Question 17

Which statement about plant cloning is correct?

Accepted Answer

Somatic cells of plants are totipotent and can give rise to all specialized cell types.

Question 18

Which of the following is NOT a typical application of DNA-based biotechnology?

Accepted Answer

Increasing the rate of natural mutations in wild populations

Question 19

A forensic scientist uses PCR and gel electrophoresis to analyze DNA from a crime scene. What is the main advantage of this approach?

Accepted Answer

It allows for rapid amplification and separation of DNA fragments, enabling identification of individuals based on genetic profiles.

DNA Tools and Biotechnology: Techniques and Applications

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