When comparing the α-globin protein in cow and humans, you find that they differ at 20 of the 165 amino acid sites in the alignment. What is the proportion of substitutions that have occurred since humans and cows diverged from each other?

A scientist is researching GS1, an enzyme with a relative molecular mass (Mr) of 78,000 present in a bacterium. The scientist has isolated two mutant strains of the bacterium as described below. Strain A: In this strain the GS1 protein is completely non-functional. Analysis of strain A shows that it produces a shortened GS1 protein with an Mr of only 38,000. Strain B: This produces functional GS1, but the Kcat is somewhat reduced. Analysis shows it produces a lengthened form of GS1, with an Mr of about 86,000. What type(s) of mutation may have occurred in the GS1 gene in strain A?

Can you check if A is correct and please help answer the following questions?

1) Use the Leontis-Westhof base pair classification to identify the interaction occurring between each of the base pairs formed in the image below: