Computing GC third codon position

Problem
You want to compute the GC content at the third codon position of protein-coding sequences already aligned. You also want to evaluate the GC-content variability of each sequence.

Solution
This is a simple problem that will help you to explore the VectorSiteContainer class. You can assess the GC-content variability using a bootstrap analysis. You have to bootstrap the whole matrix at once and store the GC content of each sequence in a matrix. Finally, you can print a summary of your analysis, for example, the mean and standard deviation of the bootstrapped GC content distribution.