Genetics is the Science of heredity and variation in living organisms. Knowledge of the
inheritance of characteristics has been implicitly used since prehistoric times for improving crop plants and animals through seletive breeding. However, the modern science of genetics, which seeks to understand the mechanisms of inheritance, only began with the work ofGregor Mendel in the mid-1800s. Although he did not know the physical basis for heredity, Mendel observed that inheritance is fundamentally adiscrete process with specific traits that are inherited in an independent manner — these basic units of inheritance are now called genes.
Following the rediscovery of Mendel''s observations in the early 1900s, research in 1910s yielded the first physical understanding of inheritance — that
genes are arranged linearly along large cellular structures called cromosomes. By the 1950s it was understood that the core of a chromosome was a long molecule called DNA and genes existed as linear sections within the molecule. A single
strand of DNA is a chain of four types of nucleotides; hereditary information is contained within the
sequence of these nucleotides. Solved by Watson and Crick in 1953, DNA''s three-dimensional
structure is a double straded helix, with the
nucleotides on each strand comoplementory to each other. Each strand acts as a template for synthesis of a new partner strand, providing the physical mechanism for the inheritance of information.
The sequence of nucleotides in DNA is used to produce specific sequences of amino acids, creating Proteins — a correspondence known as the "genetic codes". This sequence of amino acids in a
Protein determines how it folds into a three-dimensional structure, this structure is in turn responsible for the protein''s function. Proteins are responsible for almost all functional roles in the cell. A change to DNA sequence can change a protein''s structure and behavior, and this can have dramatic consequences in the cell and on the organism as a whole.
Although genetics plays a large role in determining the appearance and behavior of organisms, it is the interaction of genetics with the environment an organism experiences that determines the ultimate outcome. For example, while genes play a role in determining a person''s height, the nutrition and health that person experiences in childhood also have a large effect.
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