Problem 2 - Campbell Biology

Question

Level 1: Knowledge/Comprehension 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

Step-by-Step Solution

Answer

(B) DNA ligase-cutting DNA, creating sticky ends of restriction fragments

Step 1: Understand Electrophoresis

Electrophoresis is a laboratory method used to separate DNA, RNA, or protein molecules based on their size and electrical charge. The correct option for electrophoresis is (A).

Step 2: Understand DNA Ligase

DNA ligase is an enzyme that joins DNA strands together by forming a phosphodiester bond. It is not used for cutting DNA. Instead, restriction enzymes are used for cutting DNA and creating sticky ends. Thus, (B) is the incorrect pairing.

Step 3: Understand DNA Polymerase

DNA polymerase is an enzyme that synthesizes DNA molecules from deoxyribonucleotides, the building blocks of DNA. It is used in polymerase chain reaction (PCR) to amplify sections of DNA. The pairing (C) is correct.

Step 4: Understand Reverse Transcriptase

Reverse transcriptase is an enzyme used to generate complementary DNA (cDNA) from an RNA template. The pairing (D) is correct.

Key Concepts

Electrophoresis

Electrophoresis is a technique used to separate molecules, like DNA, RNA, or proteins, based on their size and electrical charge. This process involves placing the molecules in a gel and applying an electric field.
The negatively charged DNA or RNA molecules travel towards the positive electrode. Smaller fragments move faster and travel further through the gel than larger ones.
This method is extremely useful in DNA analysis and research, as it allows scientists to sort and identify different sizes of DNA fragments.

DNA Ligase

DNA ligase is an essential enzyme in DNA technology. It is responsible for joining DNA fragments together by forming a phosphodiester bond. This action is crucial during DNA replication and repair.
DNA ligase is not used for cutting DNA; instead, it works by sealing nicks and joining together various DNA strands.
Restriction enzymes are the tools used for cutting DNA, and they create sticky ends by making cuts at specific sequences. These sticky ends can then be joined by DNA ligase to create recombinant DNA.

• Function: Joins DNA strands
• Not for cutting DNA
• Used in DNA repair and replication

DNA Polymerase

DNA polymerase is a fundamental enzyme in the field of genetics and molecular biology. This enzyme synthesizes DNA molecules from deoxyribonucleotides, the building blocks of DNA.
DNA polymerase is critical in processes like DNA replication and PCR (Polymerase Chain Reaction). During PCR, DNA polymerase amplifies specific sections of DNA, making millions of copies of a particular DNA sequence.
This capability is crucial for various applications, such as forensic analysis, genetic testing, and research.

• Function: Synthesizes new DNA strands
• Used in DNA replication
• Key role in PCR

Reverse Transcriptase

Reverse transcriptase is an enzyme that synthesizes complementary DNA (cDNA) from an RNA template. This process is essential in the study of genes and the creation of DNA libraries.
Reverse transcriptase is used in techniques such as reverse transcription PCR (RT-PCR), where it helps convert RNA into DNA, which can then be amplified and analyzed. This method is particularly useful for studying gene expression, viruses, and retrotransposons.

• Function: Generates cDNA from RNA
• Used in RT-PCR
• Important in gene studies and viral research