Question

In the early part of the course we discussed homologies that were analogies, although highly modified, and the critical importance of homologies that were not analogies. Prove that you are a broadly trained biologist and a disciplined thinker by recounting one molecular example of each of these phenomena (e.g. two genes that are homologous and broadly analogous and two genes that are homologous but not analogous). For the latter type (homologous but not analogous), describe the evidence that establishes the homology.

Answer 1

An example of homologous and analogous genes are those for hemoglobin in vertebrates, which have a common ancestry and similar function. Conversely, Hox genes are homologous across animal phyla but not analogous, as they underlie different body plans but share a common genetic origin.

Step-by-step explanation:

The distinction between homologous and analogous genetic features is pivotal in evolutionary biology. Homologous genes share a common ancestry, while analogous genes have separate evolutionary origins but have evolved to perform similar functions due to similar selective pressures. An example of genes that are both homologous and analogous is those encoding for the hemoglobin protein in different vertebrate species; despite their diverse evolutionary paths, they perform the same function of oxygen transport.

On the other hand, genes that are homologous but not analogous include the Hox genes across different animal phyla. Although they underlie vastly different body plans and perform varied functions, their shared DNA sequences, regulatory mechanisms, and embryonic expression patterns provide strong evidence of a common ancestral gene. These homologies are not based on the function but on the detailed molecular, structural, and developmental similarities observed amongst diverse life forms.