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Ch. 20 - DNA Tools and Biotechnology
Campbell - Campbell Biology 12th Edition
Urry12th EditionCampbell BiologyISBN: 9785794169850Not the one you use?Change textbook
Chapter 20, Problem 2

Which of the following tools of DNA technology is incorrectly paired with its use?
a. Electrophoresis — Separation of DNA fragments
b. DNA ligase — Cutting DNA, creating sticky ends of restriction fragments
c. DNA polymerase — Polymerase chain reaction to amplify sections of DNA
d. Reverse transcriptase — Production of cDNA from mRNA

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1
Understand the function of each tool mentioned in the options: Electrophoresis, DNA ligase, DNA polymerase, and reverse transcriptase. Each tool has a specific role in DNA technology.
Option a: Electrophoresis is used to separate DNA fragments based on their size by applying an electric field. Smaller fragments move faster through the gel. This pairing is correct.
Option b: DNA ligase is an enzyme that joins DNA fragments by forming phosphodiester bonds. It does not cut DNA or create sticky ends; that is the role of restriction enzymes. This pairing is incorrect.
Option c: DNA polymerase is used in the polymerase chain reaction (PCR) to amplify specific sections of DNA by synthesizing new DNA strands. This pairing is correct.
Option d: Reverse transcriptase is used to synthesize complementary DNA (cDNA) from an mRNA template. This is a key step in studying gene expression. This pairing is correct.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrophoresis

Electrophoresis is a laboratory technique used to separate DNA fragments based on their size and charge. In this process, an electric current is applied to a gel matrix, causing the negatively charged DNA to migrate towards the positive electrode. Smaller fragments move faster through the gel, allowing for the visualization and analysis of different DNA sizes.
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DNA Ligase

DNA ligase is an enzyme that facilitates the joining of DNA strands together by forming phosphodiester bonds. It is crucial in processes such as DNA replication and repair, as well as in recombinant DNA technology, where it is used to connect DNA fragments. However, it does not cut DNA; that function is performed by restriction enzymes.
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Step 1) Create Recombinant DNA

Reverse Transcriptase

Reverse transcriptase is an enzyme that synthesizes complementary DNA (cDNA) from an RNA template. This process is essential in molecular biology for converting mRNA into cDNA, which can then be amplified and analyzed. It is commonly used in applications such as cloning and gene expression studies, particularly in the context of retroviruses.
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1) Initiation of Transcription