Recombinant DNA technology and vectors

Recombinant DNA technology is a set of techniques used to manipulate and transfer DNA molecules between different organisms. It involves the combination of DNA from different sources to create new genetic configurations, allowing scientists to study gene function, produce therapeutic proteins, and engineer organisms for various purposes.

In this process, a vector is an essential component. A vector is a DNA molecule that is used as a carrier to transfer a foreign DNA fragment into a host organism. It acts as a vehicle to transport the desired DNA into the host cell, where it can be replicated and expressed.

Options explanation:

a) The enzyme that cuts DNA into restriction fragments: This option refers to restriction enzymes, which are used to cut DNA at specific recognition sequences. Restriction enzymes play a crucial role in recombinant DNA technology by generating DNA fragments that can be combined with other DNA molecules. However, they are not vectors themselves.

b) The sticky end of a DNA fragment: Sticky ends are single-stranded overhangs generated by restriction enzymes when they cut DNA. These sticky ends can base-pair with complementary sequences, allowing for the joining of different DNA fragments. While sticky ends are important for DNA manipulation, they are not vectors.

c) A plasmid used to transfer DNA into a living cell: This option correctly defines a vector in the context of recombinant DNA technology. Plasmids are small, circular DNA molecules found in bacteria. They can be easily manipulated and used as vectors to transfer foreign DNA into a host cell. Plasmid vectors typically contain an origin of replication (ori) sequence, which allows them to replicate independently within the host cell.

d) A DNA fragment which carries only the ori gene: This option describes a specific type of DNA fragment but does not encompass the broader concept of a vector. While the presence of an ori gene is important for replication within a host cell, a vector typically contains additional elements such as selectable markers, promoter sequences, and cloning sites to facilitate the expression and manipulation of the inserted DNA fragment.

Conclusion:

In recombinant DNA technology, a vector refers to a plasmid used to transfer DNA into a living cell. Plasmids act as carriers, allowing the introduction of foreign DNA into host organisms for replication and expression. Understanding the role of vectors is crucial in manipulating DNA molecules and advancing various applications in biotechnology and genetic engineering.