Lecture - 2 MOLECULAR BASIS OF INHERITANCE | By Dr Rajesh sir

This lecture, delivered by Dr. Rajesh Tokriya, is the second in a series on the molecular basis of inheritance. It focuses on the chemical components of nucleic acids, specifically the sugars and nitrogenous bases. The instructor begins by reviewing the basic concept of carbohydrates, explaining that they are composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio, and that they contain aldehyde or ketone groups. He then introduces pentose sugars, which have five carbons, and illustrates the structure of ribose, a five-carbon sugar with an aldehyde group. He explains that RNA contains ribose, while DNA contains deoxyribose, which lacks an oxygen atom at the second carbon. The lecture highlights the difference in stability between DNA and RNA, attributing it to the presence of a hydroxyl group on the second carbon of ribose, making RNA more reactive and less stable. The instructor then discusses nitrogenous bases, categorizing them into purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil). He explains the structural differences, such as purines having a double-ring structure and pyrimidines a single ring, and provides mnemonics for remembering the positions of nitrogen atoms. The lecture concludes with a preview of how these components combine to form nucleotides and nucleosides.