One of the important discoveries of the 21st century is the first draft of the human genome sequence. Genome refers to all the DNA in an organism, including the genes that carry information for making proteins that the organism needs. Hundreds of researchers all around the world contributed to this discovery. The process of analyzing the data has started. One of the conclusions is that the number of genes is lower than expected, 20,000 to 25,000. The scientists noticed that 99.9 percent of DNA sequence is identical in any two organisms. This project is significant because the information from DNA can be used to develop and establish new ways to treat, cure and prevent different diseases.
An important discovery in the 20th century was the determination of DNA structure by James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins. With the help of X-ray studies of DNA, they noticed that DNA consists of two chains of nucleotides. These chains have opposite directions and a base in the center. Watson, Crick and Wilkins got a Nobel Prize for this discovery in 1962. Discovery of DNA was a milestone in the exploration of evolution. When Watson and his coworkers found out about its structure, scientists could identify that some illnesses are genetic.
Another important evolution discovery was Kary Mullis' invention of polymerase chain reaction. He found a way to turn a piece of DNA into a billion copies. He started with turning it into two and then by repeating the same action, he would again duplicate the amount of DNA. All he had to do was to change the temperature. He got a Nobel Prize in 1993. PCR is an important technique in studying evolution because scientists use it to diagnose tests, for DNA sequencing, for identifying relatives.
Charles Darwin developed the theory of evolution by natural selection in the 19th Century. Darwin and his colleague Wallace started building their theory on the behavior of pigeons and realized that the organisms that have the advantage to stay alive long enough to reproduce are those that pass on their traits frequently to their offspring. Darwin also concluded that this way these characteristic become common and the species evolve. He worked on the theory of evolution for 20 years. The 19th century is also significant because of the Mendel's laws of inheritance. Although his research was based on plants, it is applicable to humans and animals. The modern science of genetics is based on the principles of segregation and independent assortment, together with the understanding of unit inheritance and dominance.
Georges Cuvier established extinction as a fact in 1796. He started his research by studying elephant fossils and later mammal fossils. He concluded that they do not belong to any existing species and that they had disappeared. He actually thought that different time periods led to extinction of numerous species. Cuvier's theory is important to evolution because other scientists found in it a basis to work from, thus different discoveries and ideas actually come from theories that defend or criticize Cuvier's theory of catastrophe.