Two molecules of DNA are the same size, but differ in base composition. One molecule contains 20 % (A + T) while the other contains 60 % (A + T). Which molecule has the higher T m? Why?(The m is a subscript of T)

I'm not sure what T m is..or how to calculate it

T m, also known as the melting temperature, is the temperature at which half of the DNA molecules in a solution are in the double-stranded form (bound together) and half are in the single-stranded form (separated). The higher the T m value, the more stable the double-stranded DNA is.

To determine which molecule has the higher T m, we need to calculate the T m values for both based on their base composition. There are various formulas used to estimate T m, but one commonly used formula is the Wallace Rule:

T m = 4(G + C) + 2(A + T)

In this formula, G represents the number of guanine bases, C represents the number of cytosine bases, A represents the number of adenine bases, and T represents the number of thymine bases.

Let's calculate the T m of the first molecule with 20% (A + T):
- Since the molecule is composed of only two bases, it must be A and T. Therefore, the composition is 10% A and 10% T.
- Using the Wallace Rule formula, we calculate:
T m = 4(0) + 2(10) = 20

Now let's calculate the T m of the second molecule with 60% (A + T):
- Similar to the first calculation, this molecule is also composed of A and T, with a composition of 30% A and 30% T.
- Using the Wallace Rule formula, we calculate:
T m = 4(0) + 2(30) = 60

Comparing the T m values, we can see that the second molecule with 60% (A + T) has a higher T m of 60, while the first molecule with 20% (A + T) has a lower T m of 20. This means the second molecule is more stable and requires a higher temperature to separate its double-stranded DNA compared to the first molecule.