Question

Darwin used observations of homology from comparative embryology to support his hypothesis of “descent with modification.” Which of the following observations about the role of Hox genes in the development of insects and mammals are consistent with Darwin’s hypothesis?

Select all that apply. (Note that all of these statements are true, but not all of them offer support for his perspective. You’ll need to apply what you know both about Hox genes and the idea of descent with modification, to sort through them.)

A. Hox genes exist in all known animal taxa

B. Numerous duplications of Hox genes have resulted in subfunctionalization in different organisms

C. In mice, Hox genes are expressed in anterior-posterior patterns

D. Limb development in bilaterian animals is driven by Hox genes (although the exact genes may differ among these animals)

Answer 1

The correct options are:

(b) Numerous duplications of Hox genes have resulted in sub-functionalization in different organisms

(d) Limb development in bilaterian animals is driven by Hox genes (although the exact genes may differ among these individuals)

Explanation: Descent with modification literally means that offsprings inherit genes from parents but they're sometimes slightly modified to adapt to environment. So according to the question, looking for options that are consistent with Darwin's hypothesis for insects and mammals, option (b) and (d) are most relevant ones.

(a) Hox genes exist in all animal taxa- It is true but it does not give you any idea about the evolution in different organisms that can be compared. So it is true but not consistent with the hypothesis

(b) Numerous duplications of Hox genes have resulted in sub-functionalization in different organisms- When hox henes are duplicated in different places in the genome, sometimes they're integrated between a gene sequence which characterises a major function in that organism, so duplication of Hox gene there has obviously an implication; it leads to modify that organism in a certain way, so, this is consistent with the hypothesis.

(c) In mice, Hox genes are expressed in anterio-posterior patterns- This is not consistent with the hypothesis. It is just a fact.

(d)Limb development in bilaterian animals is driven by Hox genes (although the exact genes may differ among these individuals)- So talking about bilaterians, such as humans, Hox genes express in differential way, that is the reason you see individuals with different morphologies than their parents, so, this is consistent with the hypothesis.