Question 1

Which of the following best describes recombinant DNA?

Accepted Answer

DNA that has been artificially manipulated and joined from different biological sources

Question 2

A researcher wants to clone a gene of interest using a plasmid vector. Which essential feature must the plasmid have to allow for selection of bacteria that have taken up the recombinant DNA?

Accepted Answer

A selectable marker gene

Question 3

Restriction enzymes typically recognize which type of DNA sequence?

Accepted Answer

Palindromic sequences

Question 4

During a cloning experiment, a scientist uses EcoRI to cut both the vector and the insert DNA. What is the main advantage of using the same restriction enzyme for both?

Accepted Answer

It creates compatible ends for ligation

Question 5

In blue/white selection using the pUC18 vector, what does the appearance of white colonies indicate?

Accepted Answer

The bacteria contain the recombinant vector with the insert

Question 6

A scientist wants to amplify a specific DNA region using PCR. Which of the following is NOT required for a successful PCR reaction?

Accepted Answer

A selectable marker gene

Question 7

If the EcoRI recognition sequence is 6 base pairs long, and the human genome is approximately $$6.2 	imes 10^9$ base pairs, how many fragments will EcoRI generate? (Assume random distribution of bases)

Accepted Answer

$$1.5 	imes 10^6$

Question 8

Which of the following is a key difference between Southern blot and Northern blot techniques?

Accepted Answer

Southern blot detects DNA, while Northern blot detects RNA

Question 9

A cDNA library is constructed from mRNA isolated from liver cells. What information can be obtained from screening this library?

Accepted Answer

Genes that are actively expressed in liver cells

Question 10

Which of the following is a limitation of PCR?

Accepted Answer

It requires knowledge of the DNA sequence to design primers

Question 11

A researcher is using a probe labeled with $$^{32}P to $$screen a cDNA library. What is the purpose of the probe?

Accepted Answer

To hybridize to complementary sequences and identify specific clones

Question 12

Which feature of a plasmid vector allows for the insertion of DNA fragments to be cloned?

Accepted Answer

Polylinker (multiple cloning site)

Question 13

What is the role of DNA ligase in the process of recombinant DNA formation?

Accepted Answer

It seals gaps by forming covalent bonds between DNA fragments

Question 14

Which of the following vectors is best suited for cloning very large DNA fragments, such as those needed for constructing a genomic library?

Accepted Answer

Bacterial artificial chromosome (BAC)

Question 15

In the Sanger method of DNA sequencing, what is the function of dideoxynucleotides?

Accepted Answer

They terminate DNA strand elongation

Question 16

A transgenic mouse is created by injecting a recombinant DNA molecule containing a gene of interest into a blastocyst. What is a critical step to confirm successful integration of the transgene?

Accepted Answer

Screening by Southern blot

Question 17

Which of the following is a real-world application of CRISPR-Cas gene editing?

Accepted Answer

Targeted correction of genetic mutations in human cells

Question 18

During PCR, the number of DNA copies after $$n$$ cycles can be calculated using which formula?

Accepted Answer

$$2^n$$

Question 19

Why is a heat-stable DNA polymerase, such as Taq polymerase, required for PCR?

Accepted Answer

It remains active after repeated heating cycles during denaturation

Question 20

Which of the following best explains why restriction sites are often palindromic?

Accepted Answer

Palindromic sequences allow restriction enzymes to bind and cut both DNA strands at the same position

Recombinant DNA Technology: Core Concepts and Applications

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