DNA isolated from four unidentified species of bacteria - A, B, C and D has been estimated to have 38%, 26%, 24% and 12% thymine, respectively. One…
DNA isolated from four unidentified species of bacteria - A, B, C and D has been estimated to have 38%, 26%, 24% and 12% thymine, respectively. One of these four species was isolated from a hot spring (64°C). Identify the candidate which is most likely to be a thermophilic bacterium.
Select an option to attempt
Correct Answer: Option D
Explanation
Identifying the thermophile from % base composition:In double-stranded DNA, by Chargaff's rules: %A = %T and %G = %C.Given species D has 12% T: by Chargaff's rule, %A = 12%.Therefore %G + %C = 100% − 12% − 12% = 76%.This is the highest G:C content among the species listed (A, B, C, D).G:C base pairs (3 hydrogen bonds) confer greater thermostability than A:T (2 H-bonds).Higher G:C content → higher DNA melting temperature () → adapted to high-temperature environments → thermophilic.Conclusion: Species D with 76% G:C content is the thermophile.Answer: Species D.