The results of genetic studies confirmed what Gregor Mendel already published on the Mendelian theory of inheritance way back in 1865 (Mendel, 1865). Mendel was an Austrian monk who studied hereditary patterns in garden peas. He conducted several pollination and cross-pollination studies and carefully recorded the traits that were produced in the resulting progeny.
Thereafter Mendel concluded that traits are inherited based on ‘units’ (now known as genes) that are passed on unchanged to offspring; that each parent contributes a gene or unit for a certain trait and although an inherited trait may not come out in an individual, this individual still has the capacity to pass on this trait to his offspring (Mendel, 1865). These conclusions were contrary to what was believed at that time; that heredity was a ‘blending’ of parental traits.
Mendel’s conclusions were verified by the studies on the DNA structure and how it is replicated, and by the chromosomal theory of inheritance which explains that a certain gene has a copy (called an allele) from each parent, and that the trait expressed is dependent on what allele is transcribed and translated (Kornberg & Baker, 2005). Some gene copies are exactly the same; in this case the offspring will show a trait that is also shown by both parents.
The allele which can override the expression of the other dictates the trait. Other alleles, which are not expressed, are termed recessive, and can be expressed in later generations especially when the other parent has the same copy. Therefore, the knowledge of the DNA structure and how it contributes to heredity explained the observations that became the basis for the Mendelian theory of inheritance which was formulated more than a hundred years ago.
References Alberts, B. , Johnson, A., Lewis, J. , Raff, M. , Roberts, K. , & Walter, P. (2002). Molecular Biology of the Cell (4th ed. ). New York, NewYork, USA: Garland Science. Kornberg, A. , & Baker, T. (2005). DNA Replication (2nd ed. ). New York, New York: University Science Books. Mendel, G. (1865). Experiments in plant hybridization. Meetings of the Brunn Natural History Society, (pp. 3-47). Moravia. Watson, J. D. , & Crick, F. H. (1953). A structure for deoxyribose nucleic acid. Nature , 171, 737-738.