Problem 3 - Biology

Question

Human DNA and a particular plasmid both have sites that are cut by the restriction enzymes HindIII and EcoRI. To make recombinant DNA, the scientist should (a) cut the plasmid with EcoRI and the human DNA with HindIII (b) use EcoRI to cut both the plasmid and the human DNA (c) use HindIII to cut both the plasmid and the human DNA (d) a or b (e) b or c.

Step-by-Step Solution

Answer

Use EcoRI or HindIII on both plasmid and human DNA: options (b) or (c).

Step 1: Understanding Recombinant DNA

Recombinant DNA involves combining genetic material from different sources. To do this, DNA strands must be cut in a way that allows them to be joined together, generally using the same restriction enzyme on both the vector (plasmid) and the DNA to be inserted.

Step 2: Analyzing the Options

Each option represents different ways to cut the DNA: (a) cutting the plasmid with EcoRI and the human DNA with HindIII means the ends won't match. (b) using EcoRI for both ensures matching ends. (c) using HindIII for both ensures matching ends. (d) suggests using the methods in either (a) or (b), but (a) won't work because the ends won't match. (e) suggests (b) or (c), both of which would work because they use the same enzymes.

Step 3: Conclusion on Correct Options

To achieve matching ends suitable for joining, the same restriction enzyme must be used on both the plasmid and the human DNA. Thus, the correct choice involves using the same enzyme as stated in either option (b) or (c).

Key Concepts

Restriction Enzymes

Restriction enzymes play a critical role in recombinant DNA technology. They act like molecular scissors that cut DNA at specific sequences, usually known as recognition sites. These enzymes are natural defense mechanisms in bacteria, capable of destroying foreign DNA by cutting it up.

Here's how restriction enzymes work:

• They locate specific sequences of base pairs in the DNA strands, often 4-8 nucleotides long.
• Once they find their recognition site, they make a cut through the DNA.
• This cutting results in "sticky ends" or "blunt ends" depending on the enzyme. Sticky ends have overhanging strands of nucleotides, while blunt ends are straight cuts across both strands.

To create recombinant DNA, scientists typically use the same restriction enzyme to cut both the plasmid and the DNA they wish to insert. This ensures the ends are compatible and can easily join together, forming a continuous DNA chain.

Plasmid

Plasmids are small, circular DNA molecules that exist independently of chromosomal DNA in bacteria. They are key tools in genetic engineering, particularly in the creation of recombinant DNA.

Key features of plasmids include:

• They replicate independently of the bacterial chromosome, ensuring they can be maintained in high numbers within a bacterial cell.
• Plasmids often carry genes that provide beneficial traits to bacteria, such as antibiotic resistance, which can serve as selection markers in experiments.
• They can be engineered to include restriction sites, which can be cut by restriction enzymes to allow insertion of foreign DNA.

In recombinant DNA processes, a plasmid acts as the "vehicle" or vector that carries the genetic material into a host cell, where the introduced gene can be replicated and expressed. By using the same restriction enzyme to cut both the plasmid and the foreign DNA, scientists can ensure the pieces will fit together seamlessly.

Genetic Material

Genetic material refers to the DNA or RNA that contains the information necessary to build and operate an organism. It carries genes, which are sequences that code for proteins, and later proteins perform essential functions in cells and organisms.

In the context of genetic engineering, genetic material can be the genes scientists wish to insert into another organism—or vector—such as a plasmid. This process is carefully controlled:

• The target gene is isolated from the donor species' DNA.
• Both the target gene and plasmid vectors are cut with the same restriction enzyme, ensuring that the ends align perfectly due to the complementary sticky or blunt ends.
• Ligase enzymes are then used to "glue" the DNA fragments together, forming a stable recombinant DNA molecule.

This recombinant genetic material can then be inserted into bacteria or another organism to study gene function, produce proteins, or develop new traits. This simplicity in concept, coupled with the precision of molecular techniques, forms the basis of modern biotechnology.