MCAT Flashcards: Melting Temperature

What is melting temperature? Ken Tao is an MCAT expert and explains that melting temperature is the temperature at which 50% of the DNA molecules and solution are denatured. He also covers two types of base pairs: GC-base pairs and AT-base pairs. Learn more about melting temperatures in this video!

Full Transcription

In this flashcard video, we’re going to go over melting temperature.

Melting temperature is the temperature at which 50% of the DNA molecules and solution are denatured. When we’re talking about the denaturation for DNA, we’re referring to the double-stranded DNA molecules separating into two individual single-stranded DNA molecules. So the melting temperature is the temperature at which 50% of the DNA molecules and solution are separated into a single-stranded DNA molecules.

Now, the melting temperature depends on two factors. The first factor is what we call GC-content. Remember that DNA has two types of base pairs: GC-base pairs and AT-base pairs.

AT-base pairs are held together by two hydrogen bonds, whereas GC-base pairs are held together by three hydrogen bonds. What this means is the higher the percentage of GC-base pairs in your DNA sequence, the higher the melting temperature because you have more hydrogen bonds.

The second factor that the melting temperature depends on is the length of the DNA molecule. This is simply because the longer the DNA molecules, the more hydrogen bonds you have. So similarly, this means the longer the DNA molecule, the higher the melting temperature.