1.5.6 Calculating the Frequency of Nucleotide Bases

Steps for Calculating Nucleotide Base Frequencies

1. Understand Base Pairing Rules:

• The percentage of adenine (A) equals the percentage of thymine (T).
• The percentage of cytosine (C) equals the percentage of guanine (G).
• Thus, if you know the percentage of one base, you can calculate the others.

2. Using a Known Percentage:

• If $A = x\%$, then $T = x\%$.
• Similarly, $C + G = 100\% - (A + T)$.
• If $C = y\%$, then $G = y\%.$

3. Example Calculation:

• Suppose $A = :highlight[30\%]$.
• T must also be $:highlight[30\%] (A = T)$.
• Therefore, $C + G = 100\% - (A + T) = 100\% - 60\% = :highlight[40\%]$.
• If $C = :highlight[20\%]$, then $G = :highlight[20\%]$.