If Adenine makes 30% of the DNA molecule, what will be the percentage of Thymine, Guanine and Cytosine in it ?

According to Chargaff's rules of base pairing in a double-stranded DNA molecule:
1. Adenine (A) always pairs with Thymine (T), which means the percentage of Adenine is equal to the percentage of Thymine ($A=T$).
2. Guanine (G) always pairs with Cytosine (C), which means the percentage of Guanine is equal to the percentage of Cytosine ($G=C$).
3. The sum of all four nitrogenous bases in a DNA molecule is 100% ($A+T+G+C=100\%$).

Given that Adenine (A) makes up 30% of the DNA molecule:
Since $A=T$, the percentage of Thymine (T) must also be 30%.

Now, we can find the combined percentage of Adenine and Thymine:
$A+T=30\%+30\%=60\%$

This leaves the remaining percentage for Guanine (G) and Cytosine (C):
$G+C=100\%-60\%=40\%$

Since $G=C$, we divide the remaining 40% equally between Guanine and Cytosine:
$G=\frac{40\%}{2}=20\%$
$C=\frac{40\%}{2}=20\%$

Therefore, the percentages of the bases are:
Thymine (T) = 30%
Guanine (G) = 20%
Cytosine (C) = 20%