Question

Why is GC content percentage of prime nucleotides that are guanine/ cytosine included in the formula for calculating Tm?

Answer 1

Tm is the melting temperature of DNA. It is defined as the temperature at which 50% of double stranded DNA is changed to single standard DNA.

More the GC content , higher is the melting temperature because the guanine-cytosine pair is bound by three hydrogen bonds, while adenine-thymine pairs are bound by two hydrogen bonds. DNA with high GC content is more stable than with low GC content. Hence for calculating Tm, GC content is included in the formulae.

Application of GC content to determing melting temperature is useful in PCR polymerase chain reaction.