Two Competing Hypotheses to Account for the Increase in the Number

question 25

Multiple Choice

Two competing hypotheses to account for the increase in the number of Hox genes from the last common ancestor of bilaterians to the last common ancestor of insects and vertebrates are: (1) a single duplication of the entire four-gene cluster, followed by the loss of one gene, and (2) three independent duplications of individual Hox genes. To prefer the first hypothesis on the basis of parsimony requires the assumption that ________.

• A) the duplication of a cluster of four Hox genes is equally likely to the duplication of a single Hox gene
• B) there is an actual process by which individual genes can be duplicated
• C) genes can exist in spatial groupings called clusters
• D) clusters of genes can undergo disruption, with individual genes moving to different chromosomes during evolution

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