Gene a hereditary unit of life -

DNA replication

100 biotechnology and science books   

Gene 

                  Gene is particular segment of DNA. in living beings genetic information is stored in DNA. Gene is also hereditary unit that is it stores information and responsible for particular character to express in generations and pass this information from one generation to other generation. 

                It's transcription results in formation of mRNA and later this mRNA gets translated in protein. This proteins acts as enzyme Or structural component . It is said that human beings contains only near about 20000-25000 genes. In human beings genes are not present in continues fashion while it is separated by introns. 

                     Introns are intergenic sequences which separates genes. Function of introns are still unknown. If particular gene gets transfered from one generation to other as it is, results in passage of that character from one generation to other generation. One gene may code for one protein or more than one proteins. 

                  Example is eye color in human beings which is one of character present in humans. When gene gets transfered of black color of eye from one of parent to offspring it is responsible for same eye color protein expression results in same color of eyes. 

                      Other example is if trait of hair color that is present in one being gets transfered by gene with mutation to offspring then that trait is not expressed in next generation called as variation. 

                   So genes are responsible for heredity while mutation causes variation. Mutation means sudden change in genetic makeup of an individual and it's unit is muton. so this are genes responsible for us that what we are.