Why do scientists use the same enzyme to remove the insulin AND cut the plasmid open?
Scientists use the same enzyme, typically a type of restriction enzyme, to both remove the insulin gene from its original source and cut open the plasmid because it ensures compatibility and efficiency in the subsequent steps of genetic engineering.
To understand why the same enzyme is used, let's break down the process:
1. Obtaining the insulin gene: The insulin gene that codes for the production of insulin is usually sourced from another organism, such as bacteria or animals. To isolate this gene, scientists use restriction enzymes that recognize specific DNA sequences and cut the DNA at those sequences. These enzymes act as molecular scissors, allowing scientists to extract the insulin gene from the original organism's genome.
2. Preparing the vector (plasmid): A plasmid is a small, circular DNA molecule commonly used as a vector to carry foreign genes into another organism. To create a recombinant DNA molecule, the plasmid needs to be cut open so that the insulin gene can be inserted. This is where the same restriction enzyme is used. By cutting the plasmid with the same enzyme, it generates compatible and complementary sticky ends (short, unpaired DNA sequences) on both the plasmid and the insulin gene.
3. Joining the insulin gene and the plasmid: The sticky ends on both the insulin gene and the plasmid can then bind together through base pairing, creating a hybrid molecule. This is known as DNA ligation, and it is facilitated by an enzyme called DNA ligase. The ligase enzyme helps to form covalent bonds between the ends of the DNA molecules, resulting in a stable recombinant DNA molecule.
By using the same restriction enzyme for both steps, scientists ensure compatibility between the insulin gene and the plasmid. The complementary sticky ends allow for a more efficient and precise joining of the two DNA molecules, increasing the probability of successful insertion and expression of the insulin gene in the target organism.
In summary, using the same enzyme to remove the insulin gene and cut the plasmid open allows for compatibility and efficiency in the subsequent steps of genetic engineering, enhancing the success of creating recombinant DNA molecules.