Q: Which of the following equations correctly represents the hydrolysis of lactose by β-galactosidase?

$$\text{Lactose} + H_2O \xrightarrow{\beta\text{-galactosidase}} \text{Glucose} + \text{Galactose}$$

Question 1

Which of the following best describes the function of a restriction enzyme in recombinant DNA technology?

Accepted Answer

It cuts DNA at specific palindromic sequences, generating fragments with sticky or blunt ends.

Question 2

A scientist wants to clone a gene into a plasmid vector. Both the gene and the plasmid are cut with EcoRI. What is the sequence recognized by EcoRI, and what type of ends does it produce?

Accepted Answer

5'-GAATTC-3'; produces sticky ends

Question 3

Which property is NOT essential for a DNA cloning vector?

Accepted Answer

Ability to integrate into the host chromosome at a specific site

Question 4

In blue-white screening, what is the expected color of bacterial colonies that have successfully taken up a recombinant plasmid with an insert disrupting the lacZ gene?

Accepted Answer

White

Question 5

Which of the following equations correctly represents the hydrolysis of lactose by β-galactosidase?

Accepted Answer

$$	ext{Lactose} + H_2O \xrightarrow{\beta	ext{-galactosidase}} 	ext{Glucose} + 	ext{Galactose}$$

Question 6

A genomic library is constructed by:

Accepted Answer

Cutting genomic DNA with restriction enzymes and ligating the fragments into vectors.

Question 7

Which of the following statements about plasmids is FALSE?

Accepted Answer

They always integrate into the host genome during cloning.

Question 8

Why are palindromic sequences important in recombinant DNA technology?

Accepted Answer

They are the recognition sites for restriction enzymes, allowing specific DNA cleavage.

Question 9

Which of the following best explains why BACs and YACs are used instead of plasmids for some cloning applications?

Accepted Answer

They can carry much larger DNA fragments than plasmids.

Question 10

A researcher is using a Ti plasmid to introduce a gene into a plant cell. What is the main function of the T-DNA region in this process?

Accepted Answer

It integrates the foreign gene into the plant genome.

Question 11

Which of the following is a real-world example of natural cloning?

Accepted Answer

Monozygotic (identical) twins in humans

Question 12

Which step is necessary to make bacterial cells competent for transformation with plasmid DNA?

Accepted Answer

Treating cells with calcium ions and heat shock or using electroporation

Question 13

A cDNA library differs from a genomic library in that a cDNA library:

Accepted Answer

Contains only coding sequences (exons) from actively transcribed genes

Question 14

Which of the following best describes the role of DNA ligase in recombinant DNA technology?

Accepted Answer

It joins DNA fragments by forming phosphodiester bonds between adjacent nucleotides.

Question 15

A researcher is screening a DNA library to find a clone containing a specific gene. Which tool is most commonly used to identify the correct clone?

Accepted Answer

A DNA or RNA probe complementary to the gene of interest

Question 16

Which of the following vectors would be most appropriate for cloning a 250 kb fragment of human DNA?

Accepted Answer

A bacterial artificial chromosome (BAC)

Question 17

In the context of recombinant DNA technology, what is the main advantage of using an expression vector over a standard cloning vector?

Accepted Answer

Expression vectors ensure transcription and translation of the inserted gene, allowing protein production.

Question 18

Which of the following best explains why restriction enzyme recognition sites are usually palindromic?

Accepted Answer

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

Question 19

A scientist is using blue-white screening to identify recombinant clones. Which substrate is used in the agar to detect β-galactosidase activity?

Accepted Answer

X-gal

Recombinant DNA Technology: Tools, Methods, and Applications

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