History of Genetics

HISTORY OF GENETICS

The concept that living organisms inherit certain traits from their parents has been known since ancient man practiced selective breeding of plants and animals. Before Gregor Mendel, genetics had been studied but not in the detail that it was studied by Gregor Mendel. Initially, the concept was that the offspring had the average of the characteristics of the parents but this would not have made evolution possible through natural selection. This was called blending inheritance”. Remember, too, that Lamarck felt that acquired characteristics could be inherited from the parents. Pangenesis was the belief system of Darwin, who felt that both acquired and innate traits could be inherited.

Mendel himself believed that there were dominant traits and recessive traits inherited from parents. He mathematically studied pea plants and their patterns of inheritance. He wrote a paper in 1865 on the subject but this was not widely disseminated until 1900. It was discovered in 1911 by Thomas Hunt Morgan that genes were located on chromosomes. He studied fruit flies and sex-linked inheritance. Soon after, it was determined that genes lined up along a chromosome.

Chromosomes are made from DNA and related proteins but it wasn t clear that it was the DNA responsible for genetic traits. Transformation, which is the transfer of genetic material from dead bacteria or from the environment to living bacteria, was discovered in 1928.

James Watson and Francis Crick discovered the nature of DNA structure in 1953. It was determined to be a double-stranded helix. Figure 3 shows the typical structure of a DNA molecule:

Figure 3.

It was then determined that the double strands could be separated and copied in the process of DNA replication. This means that DNA is semi-conservative; one strand provides the template for the making of the other strand.