DNA and RNA Are Polymers Composed of Nucleic Acids

Nucleic acids are high-molar-mass polymers that play an essential role in protein synthesis. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acid. DNA molecules are among the largest molecules known they have molar masses of up to tens of billions of grams. RNA molecules, on the other hand, vary greatly in size, some having a molar mass of about 25,000 g. Compared with proteins, which are made of up to 20 different amino acids, nucleic acids are fairly simple in composition. A DNA or RNA molecule contains only four types of building 

In the 1940s, Erwin Chargaff studied DNA molecules obtained from various sources and observed certain regularities. Chargaff s rules, as his findings are now known, describe these patterns  

The total number of purine bases is equal to the total number of pyrimidine bases, that is, A + G = C + T. 

Erwin Chargaff (1905-2002). American biochemist of Austrian origin. Chargaff was the first to show that different biological species contain different DNA molecules. 

In 1985, a British chemist named Alec Jeffreys suggested that minisatelhte sequences provide a means of identification, much like fingerprints. DNA fingerprinting has since gained prominence with law enforcement officials as a way to identify crime suspects. 

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