Question

You are studying the source of a new virus that has recently infected humans. You suspect that the virus was transferred from oter primates (they exhibit a similar infection), specifically chimpanzees, gorillas, or orangutans. You sample blood from several infected humans and sequence some viral genes. You then build a phylogenetic tree with the human sequences and all the known strains from each primate. Draw a hypothetical phylogenetic tree that would suggest that the virus came from gorillas, and this transfer occured twice independently. Label chimp sequences (c), gorilla (g), orangutans (o), and humans (h).

Answer 1

Arming a cladogram (or phylogenetic tree) can be a little difficult. In this case you need order the organisms you want to classify. Normally their relationship is determined through characteristics such as presence or absence of appendices, physiology, habits, and nowadays molecular methods are used to determine in a better way the relationship that one organism has with another, such as the percentage of homology between DNA sequences, size of genomes, base polymorphisms among others. In this case I will make a tree based on the percentage difference between the DNA of the different primate species that are mentioned. In this case, given that the human model (Homo sapiens) is the most recent primate to this we will put it up on the tree, its closest relative is the chimpanzee (Pan panicus) because different bibliographies put the percentage of homology at least in one 99% (with differences in the decimal point). Down in the tree we could put the gorilla, given that the homology drops to 98% and finally down we could put the orangutan (gender I put) because the homology is 97%. The tree can be done in two ways. The external group can be the human or failing that the orangutan. they are only suggestions based on the percentage of homology between the species to which it infects the same virus. The ideal would be to make a tree based on how the virus sequences change when infecting each species.