A clone is a group of individuals that are genetically identical. Clones are produced by asexual reproduction or by inserting DNA from an animal's somatic cell into an egg cell that has had its nucleus (organelle) and DNA removed. In other words, we can say that a clone is a homozygote produced by asexual means. Dolly was the first animal to be cloned.

Give one significant contribution of the following scientist: H. Boyer

Sir Herbert Boyer is an American biotechnologist. Along with Stanley Cohen, he produced the first recombinant DNA molecule by fusing a gene from a bacterium with a plasmid of E. coli in 1973. He also discovered restriction enzyme endonuclease.

Explain the steps involved in the production of human insulin by recombinant DNA technology.

Human insulin is produced by the Beta cells of the islets of Langerhans of the pancreas gland. It is made up of 51 amino acids arranged in two polypeptide chains A and B. These are linked together by two disulfide bonds. A chain consists of 21 amino acids and the B chain of 30 amino acids. The gene for this protein synthesis is located on chromosome 11. In mammals, the insulin is synthesised as a pro-hormone in an inactive form which needs to be activated. The proinsulin is made of three polypeptide chains with an extra C peptide which is removed before maturation. By using rDNA technology the insulin was synthesised for the first time by Eli Lilly company as separated polypeptide strands in the plasmid of bacteria E.coli and later they were made to join together by the disulphide bonds.

Give an account of the Blue-White Method of selection of recombinants.

Recombinant DNA technology (RDT) involves several steps in a specific sequence that allows alteration of genetic material like: Isolation of DNA Fragmentation of DNA by restriction endonucleases Isolation of the desired DNA fragment Ligation of the DNA fragment into a vector Transferring the recombinant DNA into the host Culturing the host cells in a medium at a large scale Extraction of the desired product The blue-white screen is a method of selection or screening technique that allows for the rapid and convenient detection of recombinant bacteria in these experiments. Recombinant DNA (altered DNA) is inserted into a competent host cell viable for transformation. The transformed cell is then grown in the presence of X-gal. A cell transformed with vectors containing recombinant DNA will produce white colonies, cells transformed with non-recombinant plasmids grow into blue colonies. Such screening is usually performed using a suitable bacterial strain, but other organisms such as yeast may also be used.

What does PCR stand for? Describe the different steps of PCR.

PCR stands for the polymerase chain reaction. It is used to amplify copies of DNA fragments. The PCR reaction mixture contains Taq polymerase, primers, template DNA, and nucleotides (dNTPs). The three steps of PCR are denaturation, annealing, and extension. 1. Denaturation step: The reaction mixture is heated at 94 ° C to denature (unwind) the dsDNA strands. This results in the single-stranded template used for replication. 2. Annealing step: The reaction is cooled down to 55 ° C to 65 ° C. This allows the primer to bind to their complementary sequences on the single-stranded template DNA. 3. Extension: The temperature of the reaction mixture is increases to 72 ° C so that the Taq polymerase enzyme polymerizes dNTPs and form new strands of DNA by extending the primer. This cycle repeats 25 to 35 times in the entire process to amplify a small amount of DNA in multiple copies.