Proposed Number of Hox Genes in Various Extant and Extinct Animals Last Common Ancestor Last Common Ancestor of Insects and Ancestral of Bilateria

1) What conclusion is apparent from the data in the accompanying table?

A) Land animals have more Hox genes than do those that live in water.

B) All bilaterian phyla have had the same degree of expansion in their numbers of Hox genes. C) Acoel flatworms should be expected to contain seven Hox genes.

D) The expansion in number of Hox genes throughout vertebrate evolution cannot be explained merely by three duplications of the ancestral vertebrate Hox cluster.

E) Extant insects all have seven Hox genes.

Answer: D

Bloom’s Taxonomy: Applying/Analyzing

V&C Core Comp: E, I, PS

LO: 25.1

Section: 25.1 

I don’t quite understand this. Would you mind explaining to me why the answer is D? What does it mean if hox genes expand within this particular species? How do you read hox genes data to determine if their features are derived or passed on directly from common ancestor? Thank you!

Proposed Number of Hox Genes in Various Extant and Extinct AnimalsLast Common AncestorLast Common Ancestorof Insects andAncestralof BilateriaVertebratesVertebratesMammals1438 – 40

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