How to solve genetics problems (Chargaff’s rules)

Erwin Chargaff (1905-2002), an Austrian-American biochemist from Columbia University, analyzed the base composition of the DNA of various species. This led him to propose two main rules that have been appropriately named Chargaff’s rules. Rule 1 Chargaff determined that in DNA, the amount of one base, a purine, always approximately equals the amount of a particular second base, a pyrimidine. Specifically, that in any double-stranded DNA the number of guanine units equals approximately the the number of cytosine units and the number of adenine units equals approximately the number of thymine units. Human DNA is 30.9% A and 29.4% T, 19.9% G and 19.8% C. The rule constitutes the basis of base pairs in the DNA double helix: A always pairs with T, and G always pairs with C. He also demonstrated that the number of purines (A G) always approximates the number of pyrimidines (T C), an obvious consequence of the base-pairing nature of the DNA double helix. Rule 2 In 1947 Chargaff showed that the composition of DNA, in terms of the relative amounts of the A, C, G and T bases, varied from one species to another. This molecular diversity added evidence that DNA could be the genetic material. #ChargaffsRules #DNA #genetics #RNA #Guanine #Cytosine #purine #thymine #dnaReplication #chargaffsRuleOfDna #chargaffsRuleProblems #watsonAndCrick #chargaffsRuleExplained #dnaBasesPairing #complementaryBasePairing #DNASequence #dnaComplementarySequence #dnaSequenceComplementaryStrand #Adenine #andThymine #dnaSemiConservativeReplication #replicationFork #dnaReplicationSong #dnaTranscription #initiation #elongation #termination