Genes are basic unit of heredity passed from parents to child. Segment of DNA that passes genetic information from one generation to next. Gene are made up of DNA by mainly nitrogenous base, sugar and phosphate. Nitrogenous base include adenine, guanine, thymine, cytosine. Genes are found in nucleus of the cells in chromosomes. Genes help in protein synthesis and protein synthesis is done by two process known as translation and transcription. Genes are of three types:

a. Structural gene – codes for protein

b. Regulatory gene – controls other gene expression

c. Non coding gene – produce RNA molecules.

DNA is also known deoxyribonucleic acid, it carries genetic information. DNA is a double stranded ladder like structure and was first discovered in 1869. James watson and Francis crick I’m 1953 gave double helix model of DNA. DNA is made up from phosphate, sugar and Nitrogenous base (adenine, guanine, cytosine and thymine). DNA has ” semiconservative” nature which means one strand of DNA acts as template strand for the production of new strand of DNA. DNA has another property known as central dogma in which DNA converts into RNA by transcription and RNA is converted into protein by translation. DNA is organised into a structure called chromosomes. Humans have 23 pair of chromosomes in each cell which they inherit from their parents. There are three types of DNA –

a. A-DNA : right handed double helix, more compact than B

b. B-DNA : right handed double helix, most common DNA

c. Z- DNA:  left handed DNA