Similarities in protein sequence (order of amino acids) can also be used as evidence of evolution. Cells from different species that have the same proteins also suggest there is a common ancestor for both species. Cytochrome-C is a protein found in many different species.

Question

How many total amino acids are there in the sequence for human cytochrome-c?

Compare the human amino acid sequence with ONE other animal of your choice by counting the number of times an amino acid in that animal’s cytochrome-c is different from the amino acid in that same position of the human sequence.

List the animal you chose and how many differences there were.

Could this be used as evidence that humans and this animal share a common ancestor? Explain.

Answer 1

There are a total of 104 amino acids in the sequence for human cytochrome-c.

Let's compare the human cytochrome-c sequence with the cytochrome-c sequence of a chimpanzee. The chimpanzee has 2 amino acid differences compared to the human sequence.

This could be used as evidence that humans and chimpanzees share a common ancestor because the presence of only a few differences in the amino acid sequence suggests a close evolutionary relationship between the two species. The more similarities found in the protein sequence, the more likely it is that the species share a common ancestor. In this case, the minimal differences between the human and chimpanzee cytochrome-c sequences indicate a shared evolutionary history.