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

Thymine 23

Guanine 27

Step-by-step explanation:

A DNA molecule consists of two long chains of DNA connected to each other through the bonds nitrogenous bases make one with another. However, this bonding is strictly regulated through Chargaff's rule. It basically says that adenine from one DNA chain can only bond with thymine from another chain and vice versa. Additionally, cytosine from one chain only bonds with guanine from another and vice versa:

[A] = [T]

[G] = [C]

That means that there should be an equal number of corresponding bases.

If there were 23% of adenine, there will also be 23% of thymine.

Similarly, if there were 27% of cytosine, there will also be 27% of guanine.

Also note that the sum of non-bonding bases is always 50%, in this case, adenine + cytosine was 23% + 27% = 50%.