Question

Before the three-dimensional structure of DNA was discovered, scientists knew that DNA contained nitrogenous bases. The table below shows the percentages of the nitrogenous bases in a DNA sample. Which rule can be used to determine the percentages of the missing nitrogenous bases? Complete the table AND explain your answer. Base Percent Adenine 23 Thymine Cytosine 27 Guanine

Answer 1

The answer is:

1. Adenine : 23
2. Thymine : 23
3. Cytosine : 27
4. Guanine : 27

Step-by-step explanation:

Chargaff's Rule:

In 1950, Erwin Chargaff proposed the Chargaff's Rule that explains the pairing and concentration of the four nitrogeneous bases in DNA. He observed that in a DNA sample, the purines and pyrimidines existed in a 1:1 ratio. This entails that in a 100 percent sample, the percentages of the bases that bond together will be equal. This means that the percentage of adenine will be equal to that of thymine. Similarly, that of guanine will be equal to cytosine.