Biotechnology: Principles and Processes

A chimeric DNA is a recombinant DNA generated by ligating sequences derived from different sources. Gene clone is an exact copy (clones) of a particular gene or DNA sequences produced by genetic engineering techniques.

Transposons or Jumping genes are DNA sequences that can move from one location on the genome to another.

Vector shuttle is a vector which has ability to propagate in two different host species, e.g. pJDBZ19.

In Ti-plasmid, virulent gene is removed to make it vector suitable (competent) for gene transfer. In it, tumor forming virulent genes are replaced with desired genes and this way it acts as a vector to carry desired gene to a new organism where it get expressed to produce the product.

The requirements of tissue culture are hormones (auxine, cytokinin), agar-agar, inorganic salt, vitamins, amino acids, carbon source like sucrose, etc. In plant tissue culture, the medium on which explants are cultured is known as nutrient or culture medium. It acts as a source of important nutrient required for proper development of explant.

KC Mehta discovered the life cycle of black rust of wheat caused by Puccinia gramines.

P Maheshwari is renowned embryologist of India.

Cohen and Boyer for the first time made recombinant plasmid containing antibiotic resistant gene in $E$. coli.

Singer and Nicolson proposed fluid mosaic model of plasma membrane.

Virus free plants can be formed by meristem culture. The reason behind this is that virus can not propagate in rapidly dividing cells, so meristematic zone of plant always remain virus free.

Protoplast fusion technique is used for making somatic hybrids.

Somatic cell culture technique is used to propagate plants from somatic cells using nutrient medium and combination of hormones.

Callus culture Callus is undifferentiated mass of tissues. Growing callus from plant organs is callus culture.

Hairy root disease of dicot plants is caused by Agrobacterium rhizogene.

Agrobacterium tumefacians cause stem gall of coriander.

Bacillus thuringiensis is soil dwelling Gram positive bacterium, now being used as pesticide against cotton stem borer insect.

Meloidgyne incognita causes root knot disease in tomato and brinjal.

Transformation is a procedure through which a piece of DNA is introduced in a host bacterium. DNA bearing ampicillin resistance gene (transformed recipient cells) when introduced into the plate containing ampicillin will grow while DNA not bearing ampicillin resistance gene (untransformed recipient cells) will die. The genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E.coli. The normal E. coli does not carry resistance against any of these antibiotics.

Genetic code may be defined as the sequence of nucleotides in polynucleotide chain which determines the sequence of amino acids in a polypeptide chain. Thus, genetic code is universal. There is no ambiguity regarding genetic code. It means that each codon codes for the same amino acid in all organisms including bacteria, plants and animals.