Question

If the DNA sequence at the beginning and end of a gene is known, which of the following methods could be used to produce billions of copies of the gene in a few hours? a. construction of a DNA library b. reproductive eloning c. therapeutic cloning d. PCR

Short answer

d. PCR

Step-by-step solution

- Understand the Problem

The task is to find a method that can produce billions of copies of a gene in a few hours given the known DNA sequence at the beginning and end of the gene.

- List the Provided Methods

The methods provided are: a. Construction of a DNA library b. Reproductive cloning c. Therapeutic cloning d. PCR

- Evaluate Each Method

a. Construction of a DNA library: This method involves creating a collection of DNA sequences but does not rapidly amplify a specific gene.b. Reproductive cloning: This method creates a whole organism and is not used for quickly amplifying a single gene.c. Therapeutic cloning: This involves creating tissues or organs for medical purposes, not fast amplification of a gene.d. PCR: Polymerase Chain Reaction (PCR) is a technique used to amplify DNA sequences exponentially in a short amount of time.

- Select the Correct Method

Given the requirement to produce billions of copies of a gene in a few hours, the most appropriate method is PCR. PCR can exponentially amplify a known DNA sequence quickly and efficiently.

Key concepts

DNA sequence amplification

DNA sequence amplification is the process of making many copies of a specific DNA segment. It is like making photocopies of a page but much faster. This is super important for research, medical diagnostics, and many other applications. The goal is to turn small amounts of DNA into a lot, which makes it easier to study. Using special techniques, scientists can create billions of copies of a DNA sequence from just a tiny sample. When the starting and ending parts of the gene are known, this process becomes even more precise and effective. Without sequence amplification, working with DNA would be a lot harder.

Polymerase Chain Reaction

Polymerase Chain Reaction or PCR is a powerful method used to amplify DNA. Invented by Kary Mullis in 1983, it allows scientists to make millions or even billions of copies of a specific DNA sequence. Here's how it works:

• **Denaturation:** The DNA sample is heated to separate its two strands. This step breaks the hydrogen bonds between the base pairs.
• **Annealing:** The mixture is then cooled, allowing primers to bind to their complementary sequences on the DNA strands. Primers are short DNA segments that initiate the replication process.
• **Extension:** DNA polymerase adds nucleotides to the primers, creating new DNA strands. This process doubles the amount of DNA.

These steps are repeated 20-40 times in a machine called a thermal cycler. Each cycle doubles the DNA amount, leading to exponential amplification. PCR is used in genetic testing, forensics, research, and many other fields.

gene cloning

Gene cloning is a method used to make copies of specific genes. Though it sounds similar to PCR, the processes and outcomes are different. Gene cloning involves inserting a gene into a plasmid, a small circular DNA molecule. Here is how it works:

• **Isolation:** The gene of interest is isolated from the DNA.
• **Insertion:** The isolated gene is then inserted into a plasmid using an enzyme called ligase. This plasmid, now carrying the target gene, is known as a recombinant plasmid.
• **Transformation:** The recombinant plasmid is introduced into bacteria or another host cell. Inside these cells, the plasmid replicates along with the cell's own DNA.
• **Selection:** Cells that have successfully taken up the recombinant plasmid are selected and grown to produce many copies of the gene.

Gene cloning is useful for producing proteins, studying gene function, and creating genetically modified organisms. Unlike PCR, it is not used for rapid replication within hours, but it provides a stable and lasting source of the desired gene.

rapid DNA replication

Rapid DNA replication methods help create large amounts of DNA in a short period. PCR is the most famous technique for this purpose. PCR can create billions of DNA copies in just a few hours, making it a go-to method. Here’s why it’s so effective:

• **Speed:** Each PCR cycle can be completed in just a few minutes. With multiple cycles, it quickly ramps up the DNA count.
• **Precision:** Knowing the beginning and end sequences of the DNA target allows for specific amplification, reducing errors.
• **Efficiency:** Even a small amount of starting material can produce large quantities of DNA.

Before PCR was invented, amplifying DNA sequences was a slow and tedious process. Now, rapid DNA replication techniques like PCR have revolutionized fields such as molecular biology, genetics, and medical diagnostics. They allow scientists to work with ample amounts of DNA, which accelerates research and helps in various applications like crime scene investigations and disease diagnosis.