Biotechnology : Principles and Processes — NCERT Solutions

A reporter enzyme can help identify transformed host cells by producing a visible signal, such as a colour change, when a suitable substrate is present. The chapter gives the example of β-galactosidase: if the foreign DNA is inserted into its coding sequence, the gene becomes inactivated and the colony does not produce blue colour. Thus, colonies that remain coloured are non-recombinants, while non-coloured colonies indicate successful transformation with foreign DNA. This can be used along with a selectable marker to monitor transformation.

(a) Origin of replication (ori): It is the specific DNA sequence from where replication starts. Any DNA linked to this sequence can replicate inside the host cell, and this sequence also helps control the copy number of the linked DNA.

(b) Bioreactors: These are vessels in which raw materials are biologically converted into specific products using microbial, plant, animal, or human cells. They provide optimal conditions such as temperature, pH, oxygen, salts, vitamins, and substrate, and are used for large-scale production.

(c) Downstream processing: After the biosynthetic stage, the product must be separated, purified, formulated with suitable preservatives, and tested for quality before marketing. These post-production steps are collectively called downstream processing.

(a) PCR: PCR stands for Polymerase Chain Reaction. It is a method used to make many copies of a gene or DNA segment in vitro using primers and DNA polymerase. The process includes three steps in each cycle: denaturation, primer annealing, and extension. Repeated cycles can amplify DNA to about billion-fold.

(b) Restriction enzymes and DNA: Restriction enzymes are endonucleases that cut DNA at specific recognition sequences, often palindromic sequences. They cut the two strands at specific points to produce fragments, usually leaving sticky ends. These fragments can then be joined by DNA ligase to form recombinant DNA.

(c) Chitinase: Chitinase is an enzyme used to break down chitin, the material present in fungal cell walls. It is used during isolation of DNA from fungal cells to help break open the cells and release the genetic material.