Genetics is defined as the study of genes through their variation or the study of inheritance.

GENETICS

Genetics is defined as the study of through their variation or the study of inheritance. It is the branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms.

For thousands of years farmers and herders have been selectively breeding their plants and animals in order to produce more productive . It was somewhat of a hit or miss process since the actual mechanisms governing inheritance were unknown. Knowledge of these genetic mechanisms finally came as a result of careful laboratory breeding experiments carried out over the last century and a half.

By the 1890's, the invention of better microscopes allowed biologists to discover the basic facts of cell division and sexual reproduction. The focus of research then shifted to understanding what really happens in the transmission of hereditary traits from parents to children. A number of hypotheses were suggested to explain heredity, but Gregor Mendel, a little known Central European monk, was the only one who got it more or less right. His ideas had been published in 1866 but largely went unrecognized until 1900, which was long after his death. His early adult life was spent in relative obscurity doing basic genetics research and teaching high school mathematics, physics, and Greek in Brno (now in the Czech Republic). In his later years, he became the abbot of his monastery and put aside his scientific work.

While Mendel's research was with plants, the basic underlying principles of heredity that he discovered also apply to people and other animals because the mechanisms of heredity are essentially the same for all complex life forms.

Through the selective growing of common pea plants over many generations, Mendel discovered that certain traits show up in offspring plants without any blending of parent characteristics. For instance, the pea flowers are either purple or white--intermediate colors do not appear in the offspring of pea plants. Mendel observed seven traits that are easily ...

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flower color is purple or white
flower position is axil or terminal
stem length is long or short
seed shape is round or wrinkled
seed color is yellow or green
pod shape is inflated or constricted
pod color is yellow or green

This observation that there are traits that do not show up in offspring plants with intermediate forms was critically important because the leading theory in biology at the time was that inherited traits blend from generation to generation. Most of the leading scientists in the 19th century accepted this "blending theory." Charles Darwin proposed another equally wrong theory known as "pangenesis". This held that hereditary "particles" in our bodies are affected by the things we do during our lifetime. These modified particles were thought to migrate via blood to the reproductive cells and subsequently could be inherited by the next generation. This was essentially a variation of Lamarck's incorrect idea of the "inheritance of acquired characteristics."

Mendel picked common garden pea plants for the focus of his research because they can be grown easily in large numbers and their reproduction can be manipulated. Pea plants have both male and female reproductive organs. As a result, they can either self-pollinate themselves or cross-pollinate with another plant. In his experiments, Mendel was able to selectively cross-pollinate plants with particular traits and observe the outcome over many generations. This was the basis for his conclusions about the nature of genetic inheritance.

He came to three important conclusions from these experimental results:

That the inheritance of each trait is determined by "units" or "factors" (now called ) that are passed on to descendents unchanged
That an individual inherits one such unit from each parent for each trait
That a trait may not show up in an individual but can still be passed on to the next generation.