Question 1

The isolation and copying of a gene, usually in large quantities is called gene cloning.

Accepted Answer

Gene cloning involves isolating and copying a gene, usually in large quantities.

Question 2

Cloned genes may be mutated outside of a cell by a process called site-directed mutagenesis.

Accepted Answer

Site-directed mutagenesis is a laboratory technique that allows for specific changes (mutations) to be made to a cloned gene sequence. This process occurs outside of a cell, in a test tube or other laboratory setting.

Question 3

A vector is a small segment of DNA that a gene of interest is inserted into for cloning.

Accepted Answer

This is correct. A vector is a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell, where it can be replicated and/or expressed. This foreign genetic material can be a gene of interest for cloning.

Question 4

cDNA is made from mRNA therefore, it lacks introns and contains only the coding sequence for the functional protein.

Accepted Answer

cDNA is made by reverse transcription of mRNA and therefore lacks introns, which are non-coding regions of DNA present in the original genomic DNA. This allows for expression of only the coding sequence of the gene in the final protein product.

Question 5

Which of the following is a step in a PCR?

Accepted Answer

PCR (Polymerase Chain Reaction) is a technique used to amplify a specific segment of DNA. The steps in PCR are as follows:

1. Denaturation: The double-stranded DNA is heated to a high temperature (around 95°C) which breaks the hydrogen bonds between the two strands, separating them into single strands.

2. Annealing: The temperature is lowered (around 50-60°C) and a short segment of single-stranded DNA called a primer is added. The primer binds to the complementary sequence on the single-stranded DNA.

3. Extension: A DNA polymerase enzyme is added along with nucleotides (building blocks of DNA) and the temperature is raised to the optimal temperature for the polymerase. The polymerase uses the primer as a starting point and begins to copy the single-stranded DNA into a double-stranded DNA molecule.

The correct answer is therefore B as it describes the annealing step where the primers bind to the complementary sequences on the template DNA. The other choices, cooling to break hydrogen bonds (A), DNA gyrase enzyme (C), and DNase I (D) are not steps in PCR.

Question 6

You are using CRISPR-Cas technology to introduce a single nucleotide change in a gene of interest in living cells. You are designing your experiment. In which component of the reaction will you engineer the single nucleotide change?

Accepted Answer

The donor DNA is the component that contains the desired nucleotide change and is used to replace the existing sequence in the gene of interest during CRISPR-Cas editing. Therefore, engineering the single nucleotide change into the donor DNA will be the most effective way to introduce the desired change into the living cells.

Question 7

A researcher is interested in whether or not a transcription factor binds to a specific site on a strand of DNA. However, the samples accidentally contain SDS. What will the gel mobility shift assay results show?

Accepted Answer

SDS (sodium dodecyl sulfate) is a detergent that denatures proteins by disrupting non-covalent bonds, which would prevent the transcription factor from binding to the DNA. Therefore, the presence of SDS in the samples would lead to a scenario where the protein does not bind to the DNA, and the movement of the DNA through the gel would not be affected, as the DNA's mobility is determined by its size and charge, not by protein binding in this context.

Question 8

What technique can be used to determine DNA-protein interactions?

Accepted Answer

DNAse I foot printing is the best technique to determine DNA-protein interactions because it involves digesting the DNA with DNAse I in the presence of the protein of interest, which protects certain regions of the DNA from digestion. This results in a pattern of fragments that can be visualized by gel electrophoresis, revealing the specific regions of the DNA that are bound by the protein. Western blotting and PCR are not suitable for this purpose, as they do not directly measure protein-DNA interactions. Restriction enzyme analysis may be useful for studying DNA sequence variations, but it does not provide information about protein binding.

Question 9

The DNA Pol III enzyme can use mRNA to make a cDNA strand.

Accepted Answer

DNA Pol III is a DNA polymerase enzyme that can only synthesize a new DNA strand using a template DNA strand. It cannot use an mRNA template to make a new cDNA strand. This is a function of reverse transcriptase enzymes.

Question 10

R factors typically contain genes for antibiotic resistance.

Accepted Answer

R factors are plasmids that often carry genes for antibiotic resistance, making them significant contributors to the spread of antibiotic resistance among bacteria.

Question 11

The polymerase used in PCR reactions is derived from the thermophile organism Thermus aquaticus.

Accepted Answer

The polymerase used in PCR reactions is Taq polymerase, which is derived from the thermophile organism Thermus aquaticus.

Question 12

Dideoxy nucleotides are used in which technique?

Accepted Answer

Dideoxy nucleotides are used in DNA sequencing to terminate the elongation of DNA strands at specific nucleotides. This allows for the determination of the order of bases in a DNA sequence.

Question 13

Antibodies can be used as a probe for which technique?

Accepted Answer

Antibodies can be used in Western blotting, where they are used to detect the presence of a specific protein in a sample. Northern blotting and Southern blotting are used to detect RNA and DNA, respectively, and do not typically utilize antibodies. Eastern blotting is not a commonly used technique.

Question 14

Molecular biologists use restriction enzymes to amplify a specific section of DNA within the genome.

Accepted Answer

Molecular biologists typically use polymerase chain reaction (PCR) to amplify a specific section of DNA within the genome. Restriction enzymes are used to cut DNA at specific sites, but they do not amplify DNA.

Question 15

A scientist does not have an antibody to detect the protein of interest, but wants to know if the gene is expressed at low levels. What technique could the researcher use to detect, but not quantify the expression of the gene of interest?

Accepted Answer

Reverse transcriptase PCR (RT-PCR) can be used to detect the presence of RNA transcripts from the gene of interest, even if they are present at low levels. This technique involves reverse transcribing RNA into cDNA, which can then be amplified using PCR. The resulting PCR products can be visualized on an agarose gel to confirm the presence of the gene of interest.

Question 16

Mutations generated during site-directed mutagenesis occur randomly in the genome.

Accepted Answer

Site-directed mutagenesis is a technique used to introduce specific and targeted mutations in the genome at a particular site. Therefore, the mutations generated during site-directed mutagenesis are not random, but rather deliberate and intentional.

Quiz 21: Molecular Technologies