 The important experiments in the field of biochemistry and genetics laid down the foundation of molecular biology. The most important experiments among those were the description of DNA structure by Watson and Crick and in the field of genetics, the main experiments which contributed towards the development of molecular biology were the experiments of Avery who proved that DNA is the genetic material. So these experiments, they actually laid down the foundation of molecular biology. Now the molecular biology was born and the new discoveries were being made in the field of molecular biology. So the question was how DNA is expressed, how it transfers its information in the form of proteins. So this problem was solved in 1957 by Francis Crick who laid out the central dogma of molecular biology and this central dogma foretold the relationship between DNA, RNA and protein. It described how DNA transfers its information to RNA and then this information is translated in the form of proteins. So here in this illustration you can see the DNA molecule. The information in the DNA molecule is copied to the mRNA molecule and then this information is translated from mRNA to the proteins. So the information which is present in DNA molecule is exactly copied in the form of protein molecule. So in this way this information is carried from the nucleus from the DNA molecule and it is transmitted to the site of protein synthesis where this information is translated in the form of protein synthesis. Next important discovery was made in 1958 by Matthew Macilsen and Franklin Stahl. They proved that the replication in a DNA molecule was semi-conservative because this was another important problem that how a DNA molecule is replicated into two molecules and then into four molecules. So in this picture you can clearly see this is a DNA molecule and when it replicates one strand goes to this molecule and the other strand goes to this molecule. So both the blue strands here and here they are parental strains. They have come from the parental molecule of DNA and the pink strands they are synthesized new. So this is called semi-conservative that is one strand is conserved. In the next replication again from this molecule one strand is conserved and the other strand is newly synthesized. So this is called semi-conservative replication and this was described by Matthew Macilsen and Franklin Stahl. Next important contribution was made by Marshall Nirenberg and Gobind Khurana. They work independently and they cracked the code in early 1960s. They found that three bases constitute a code word called a codon that stands for one amino acid. It means the three words on the strand of DNA they code for one amino acid. So in this way all the information for the synthesis of proteins containing 20 different types of amino acids is present in the DNA molecule in the form of codons. Next in 1970s the important achievement was gene cloning. Scientists have learned to isolate genes from some organisms, place them in new organisms and reproduce them by a set of techniques which is called gene cloning. So in this way the genes, the characteristics from one organism can be transferred to the other organism. It was an important achievement in the field of molecular biology and it gave rise to the genetic engineering. So with the help of this gene cloning and genetic engineering many genetically modified organisms were created and these organisms included plants and animals and many of these genetically modified organisms are in practice, they are in the field and still many new are being created. So the new organisms, genetically modified organisms they have desirable characteristics. As you desire you can produce those characters in the GMOs. The important contribution, perhaps the most important contribution in the field of molecular biology is the human genome project. The human genome project was launched in USA in 1990 and was completed in 2003. The main goal of human genome project was to sequence the whole genome of the human and to identify and to map all the genes present in the human genome. There are approximately 35,000 genes present in the complete human genome. Although this human genome project it was successful to the extent that it sequenced all the genome of human beings and it mapped all the genes present in this genome but many of the genes are still undescribed. That is the functions of those genes is still to be described.