Which came first, a hen or an egg? Is a classical question. On the same pattern you can think about creation of magic molecules of nucleic acids, RNA and DNA. The confinement to these and other organic molecules that we call them today might have been provided with a cell membrane resulting into the formation of procaryotic cells. The endosymbiosis, perhaps, led to formation of eucaryotic cells and their organelles. As a manager is to an industry so a nucleus is to the cell. A manager of a good industry cannot be willy-nilly. He keeps up the constitution and rules and regulations. In the same way working of a cell goes on, as directed by genetic material, the DNA which has been called a blue print of life. Some special haploid cells might have ogled at other haploid cells under special circumstances resulting their union and formation of diploid cells.
    Dear students, there is an option for changes but good changes alone sustain. You just can think over how difficult it might have been for Darwin to propel his theory, which we call Darwinism, against strict Catholic demagogues. Some people also argue by saying that he was the son of a VIP and enjoyed royal patronage. But it was not the fact. He chose the hard facts by his observations in nature.
    In 1900 almost 16 years after the death of Gregor Mendel, three plant breeders Hugo De Vries, Karl Correns, and Erich Tshermark who had worked independently confirmed the significance of Mendel's forgotten work.
    The new techniques in the field of molecular biology have opened new vistas of biotechnology and genetic engineering, e.g. electrophoresis through a gel separates the DNA and RNA molecules according to size; restriction endonucleases can cleave DNA molecules at particular sites as DNA fragments can be digested with an endonuclease; DNA hybridization can be used to identify specific DNA molecules; hybridization probes can identify electrophoretically separated DNA and RNAs; specific segments of DNA can be isolated, DNA can be cloned (in plasmid vectors); vector DNA can be introduced into host organisms by transformation; libraries of DNA molecules can be created by cloning; hybridization can be used to identify specific clone in a DNA library; short custom-designed segments of DNA called oligonuolectides can be synthesized; the polymerase chain reaction (PCR) can amplify DNAs by repeated rounds of DNA replication in vitro; in forensics if a criminal's DNA contains a Polymorphism (the alternate DNA sequences) which is present in DNA found in the scene of crime, the criminal can be detected.
    To conclude, I would like to say that you will find "Cytology, Genetic and Evolution" a guiding star in understanding the secrects of life. Of course, it has been written primarnily to meet out the requiremants of a paper for the course of B.Sc.
 

PURSHOTAM KAUSHIK