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 a dog 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

Human cytochrome-c contains a total of 104 amino acids.

For example, let's compare the human cytochrome-c sequence with a dog. If we find that there are differences in 10 out of the 104 positions, this could be used as evidence that humans and dogs share a common ancestor. The more similarities in the amino acid sequence, the closer the genetic relationship between the two species. The fact that both species have the same protein, cytochrome-c, and share some similarities in their amino acid sequences suggests a common evolutionary origin.