Lecture 16 Topic: Genetic Engineering. Cloning of cells, genes and organisms. Gene library and gene bank.

Plan of the lecture:

1. Meaning of genetic Engineering.

2. Practical Applications of Genetic Engineering.

3. Cloning of cells, genes and organisms.

4. Gene library and gene bank.

5. Transgenic organisms.

Genetic engineering is the manipulation of genes by man. It refers to artificial synthesis, isolation, modification, combination, addition and repair of the genetic material (DNA) to alter the phenotype to suit human needs. It has evoked a great interest because it may some day enable the geneticists to set right the disease-causing genes for the improvement of human race, and even to create life.

Genetic engineering developed in the early 1970s, and now one of the most fertile areas of genetics.

The discovery of two items gave the idea of genetic engineering:

1) Plasmids, the additional DNA bodies in a bacterial cell, that replicate along with the chromosomal DNA.

2) Restriction Endonucleases, specific en­zymes that cut DNA at particular sites.

Techniques of Genetic Engineering

Old Techniques. Use of microbes to prepare wine and cheese, and selective breeding (hybridiza­tion) of plants and animals to change the genotype and phenotype of the hybrids are the oldest and the most widely used techniques of genetic engineering.

New Technique. Now new techniques have been developed to manipulate the genetic material. Genetic engineering was started in 1973 by two scientists of USA : Stanley Cohen and Herbert Boyer, by combining a gene from a bacterium with the plasmid of E. coli. Since then, genetic engineer­ing techniques have been used for many purposes useful to humans. The use of living organisms or their components

a) to improve human health,

b) to produce genetically modified organisms, and

c) to produce beneficial materials, such as enzymes, hormones, vaccines, etc., is known as biotechnology. The new technique of genetic engineering is known as recombinant DNA technology.

Recombinant dna Technology

Recombinant DNA technology involves two basic processes:

1) formation of recombinant DNA and

2) introduction of recombinant DNA into an appropriate host. Recombinant DNA is the DNA formed by combining DNAs from different or­ganisms. For instance, insulin gene cut off from rat's DNA and linked to a bacterial plasmid gives recom­binant DNA. Formation of recombinant DNA re­quires a skilful handling of the genetic material and, therefore, the term genetic engineering is used for it. The properties of DNA which help in the forma­tion of recombinant DNA are denaturation and renaturation.

Denaturation is the separation of the two strands of DNA by breakdown of hydrogen bonds on heating.

Renaturation is the reunion of complementary strands to form DNA duplex on cooling. Thus, the single strands of DNA from dif­ferent sources can join if there are segments having complementary base pairs.