Emily Law Hoi-tung, 17 SKH Bishop Mok Sau Tseng Secondary School The discovery of penicillin. In 1928, Sir Alexander Fleming observed that some bacteria were destroyed by the mould Penicillium notatum. When put to medical use, penicillin proved to be a miracle in world war two by preventing infection in wounds - the biggest wartime killer. Millions of lives have been saved by it since then. Penicillin is still used today to heal wounds. If it had not been discovered, people would suffer from infections a lot more. Mandy Chu Ka-man, 17 SKH Bishop Mok Sau Tseng Secondary School The discovery of DNA. Watson and Crick proposed the notion of the double helix molecular model for DNA in 1953. This was the starting point from which scientific research on DNA and genetics grew in the latter half of the 20th century. The discovery enables us to understand genetic diseases and develop genetically modified foods - and even clones. Different types of technology have been developed because of the discovery. Some of them bring benefits while others may be harmful to us. It is a field worth exploring. Janet Tang Man-wai, 17 SKH Bishop Mok Sau Tseng Secondary School The discovery of DNA, which carries the genetic information that makes us what we are. These genetic materials are unique and determine the characteristics of organisms. Criminals can be identified by analysing the DNA in blood, hair, saliva and tears. Apart from that, DNA is used in genetic engineering, which helps increase crop yields. This is especially important for regions of the world where there are food shortages. Willa Chan Choi-fong, 16 Tak Oi Secondary School Gene mapping. The Human Genome Project was made possible by Watson and Crick's discovery of the DNA double helix. The project's objective was to sequence all the genomes in a human. Gene mapping was the first stage and was completed in 1995. It revealed the fundamental genetic structure of humans. By recording the codes of all the genes, scientists can now tell which gene controls which characteristic, enabling us to discover cures for genetic diseases.