Greor Mendel, "The Father of Genetics", discovered the basic principles of heredity by breeding garden peas in carefully planned experiments. He chose to work with pea plants because they had many traits that existed in two forms and because they produced large numbers of offspring quickly. Mendel concluded from his experiments that each plant contains two factors for a particular trait, one passed down from the male parent and one from the female parent. These factors known as genes are the genetic information that codes for a specific trait and are located on different segments of chromosomes.


In the first of Mendel's experiments, a tall purebred pea plant (TT) was crossed with a short purebred pea plant (tt). The result of this cross was all tall hybrid pea plants (Tt). When these second-generation plants were crossed, the result was one tall (TT) purebred; two tall (Tt) hybrids; and one short (tt) purebred. Mendel concluded that tallness in pea plants was dominant, and became the expressed trait, (uppercaseT). The shortness in the pea plant was recessive, becoming the hidden trait (lower case t) if paired with a dominant allele. Letters or symbols representing an organismís genetic make-up are the genotype = TT, tt, Tt. The phenotype would be its physical appearance, either tall or short.


In order to fully understand the science of genetics, one must be aware that every human cell contains a nucleus, within which lie the 46 human chromosomes (or 23 pairs), which determine each individual's unique genetic makeup, as we investigated through our fingerprints. Recall a karyotype is like a cellís organizational chart of its chromosomal make-up arranged by like numbers, sizes, and types. Scientists can tell a lot from our chromosomal make-up, for instance which traits we will exhibit, if we are male (x,y) or female (x,x), and if we will inherit any genetic disorders. Chromosomes are made up of DNA, the blueprints for our life. DNA encodes all the materials needed to make up our bodies as well as the instructions for how to run it. DNA is found in all cells, and its structure is basically like an alphabet that has a four-letter repeating pattern throughout its very long molecule strand. Today DNA profiling is a very important tool for forensic scientists. It can aid in identifying potential crime suspects, exonerate wrongly accused persons, establish paternity relationships, and authenticate valuable consumables or pedigree breeds.