Arrange the following DNA samples in ascending order of their melting temperature (Tm)?
i. DNA with 13% T
ii. DNA with 26% T
iii. DNA with 30% T
iv. DNA with 20% T
The correct option is D iii, ii, iv, i
Tm is the temperature at which half of the DNA duplex is denatured. Tm is directly proportional to G-C content.
Tm is less for DNA with high A/T content because A and T are bound by a double hydrogen bond while G and C are bound by a triple hydrogen bond which makes it stronger and difficult to break..
So, DNA with 30% T would have lowest Tm.