Question

At ________ 50% of the strands have been unwound (Higher Tm, higher GC %)

A) Melting temperature
B) Annealing temperature
C) Denaturation temperature
D) Replication temperature

Answer 1

At melting temperature (Tm), 50% of the DNA strands have been unwound. The higher the GC content of the DNA, the higher the melting temperature will be.

Step-by-step explanation:

At melting temperature (Tm), 50% of the strands have been unwound, meaning that half of the double-stranded DNA has separated into single strands. This process occurs at high temperatures, typically ranging from 80 to 90 degrees centigrade for DNA. The percentage of guanine (G) and cytosine (C) bases—collectively known as GC content—affects the melting temperature, with higher GC content leading to a higher Tm due to the stronger bonding between G and C bases compared to adenine (A) and thymine (T) bases. The process of denaturation and renaturation is useful in techniques such as Polymerase Chain Reaction (PCR), where DNA is repeatedly heated to denature it, cooled to allow primers to anneal, and then heated again for DNA polymerase to extend the primers.