The Following Questions Refer to the Description Below

question 35

Multiple Choice

The following questions refer to the description below.
All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.
-The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information, which explanation is most likely?

• A) Pax-6 in all of these animals is not homologous; it arose independently in many different animal phyla due to intense selective pressure favoring vision.
• B) The Pax-6 gene is really not "one" gene. It is many different genes that, over evolutionary time and due to convergence, have come to have a similar nucleotide sequence and function.
• C) The Pax-6 gene was an innovation of an ancestral animal of the early Cambrian period. Animals with eyes or eyespots are descendants of this ancestor.
• D) The perfectly designed Pax-6 gene appeared instantaneously in all animals created to have eyes or eyespots.

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Definitions:

React

To undergo a chemical change or transformation in response to another substance or condition.

Sodium Chloride

The chemical name for table salt, a compound with the formula NaCl, widely used as a condiment and preservative.

Sodium

A soft, silver-white, highly reactive metal belonging to the alkali metal series in the periodic table, denoted by the symbol Na.

Calcium Carbonate

A white, insoluble solid (CaCO3) occurring naturally as chalk, limestone, marble, and forming the shells of sea creatures.