Forelimbs Form at the Junction of the Neck and Thoracic

question 47

Multiple Choice

Forelimbs form at the junction of the neck and thoracic vertebrae,the position of which is controlled by HoxC-6 genes.Several kinds of vertebrates from different classes are limbless,including limbless lizards,and amphibians known as caecilians.All descended from limbed forms.On the basis of recent research in genetics,what would you conclude about the functioning of their HoxC-6 genes?

• A)The site of expression of their HoxC-6 genes may have moved anteriorly until the level of expression has eliminated the neck region.
• B)The site of expression of their HoxC-6 genes would be the same as that of limbed vertebrates but is simply turned off early in development.
• C)Their HoxC-6 gene has mutated and serves a different function than in limbed vertebrates.
• D)The effect of the HoxC-6 gene is masked by another gene that is dominant to it.

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Definitions:

Projective Measures

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Study of Personality

The branch of psychology that focuses on understanding individual differences in behavior, emotion, and thought patterns.

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The scientific study of animal behavior, often with a focus on behavior under natural conditions.