History of genetics (Mendel)

• Until about 150 years ago, people had no idea how genetic information was passed from one generation to the next
• Today, people can predict the outcome of a single genetic cross
• Gregor Mendel


  An Austrian monk who first worked out the patterns of genetic inheritance
• Mendel's experiments


  1. Used smooth peas, wrinkled peas, green peas and yellow peas

  2. Cross-bred the peas and counted the different offspring carefully

  3. Found that characteristics were inherited in clear and predictable patterns
• Mendel's theory


  • There were separate units of inherited material
  • Some characteristics were dominant over others and never mixed together
• Mendel published his findings in 1866
• Mendel's work was not understood at the time as people did not know about genes or chromosomes
• Mendel's work was finally accepted 16 years after his death in 1884
• Development of genetics


  1. People saw chromosomes through a microscope and observed 'the dance of the chromosomes' during cell division

  2. Other scientists discovered Mendel's papers and repeated his experiments, giving him credit
• In the early 20th century, scientists observed that chromosomes and Mendel's units of inheritance behaved in very similar ways
• It wasn't until the 1950s that scientists finally put together the evidence to show that DNA is the material of inheritance and to explain how it works
• Maurice Wilkins and Rosalind Franklin in London were looking at the structure of DNA using X-rays, while James Watson and Francis Crick at Cambridge were trying to build a 3-D model of DNA
• The Cambridge team came up with the double helix structure for the DNA molecule, using Rosalind Franklin's X-ray results released without her permission by Maurice Wilkins
• The gene theory states that genes code for proteins and this is how they have their effect
• As scientists begin to understand more about how the environment can affect the proteins made by a particular gene, knowledge is moving forward again
• The fundamental understanding of genetics and some of the most common genetic diseases that affect people is still based in the work of Gregor Mendel all those years ago