Almost all extant animals have Hoxgenes that are involved in body patterning. Ho

Question

Almost all extant animals have Hoxgenes that are involved in body patterning. How might differential expression of and regulation by Hox genes contribute to mosaic evolution in which different segments of an animal body plan evolve different morphologies? What can we infer about the common ancestors of living animals based on the presence of these genes? Why do organisms that are incredibly distinct morphology, with complete different body plans, use so many of the same patterning genes? How can these same genes produce very different responses, ? in different tissues of one organism and (ii) in different organisms? a. b. c. d.

Explanation / Answer

a) The order in which individual genes are expressed along the head-to-tail axis of the embryo mirrors the physical order of the Hox genes within the Hox cluster. This is a “spatial” and “temporal” issue where different genes control different morphologies at different parts of the body using differente regulatory mechanisms.

b) We can infer that these genes are present in the ancestors of the living animals because of their omnipresence in the current animal species.

c) Because this are ancient genes that had suffered molecular selection and survived during millions of years

d) (i) In different tissues using time differential expression

(ii) In different organism using different regulatory mechanisms

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