Table 321 Proposed Number of Hox Genes in Various Extant and and Extinct

question 41

Multiple Choice

Table 32.1. Proposed Number of Hox Genes in Various Extant and Extinct Animals

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

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Definitions:

Eugenics Movement

A historical campaign aimed at improving the genetic quality of the human population through selective breeding and, at times, the sterilization of individuals deemed genetically undesirable.

Sterilization

A process designed to eliminate all forms of life, including microorganisms, from an object or environment.

Intellectual Disability

A condition characterized by significant limitations in both intellectual functioning and adaptive behavior, which covers many everyday social and practical skills.

Adaptive Skills

Skills that enable an individual to meet the demands of everyday life effectively, including social, practical, and emotional skills.