Pax-6 usually causes the production of a type of light-receptor pigment. In vertebrate eyes, though, a different gene (the rh gene family) is responsible for the light-receptor pigments of the retina. The rh gene, like Pax-6, is ancient
In the marine ragworm, for example, the rh gene causes production of c-opsin, which helps regulate the worm's biological clock. Which of the following most likely accounts for vertebrate vision? A) The Pax-6 gene mutated to become the rh gene among early mammals.
B) During vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments.
C) In animals more ancient than ragworms, the rh gene(s) coded for visual receptor pigments; in lineages more recent than ragworms, rh has flip-flopped several times between producing biological clock opsins and visual receptor pigments.
D) Pax-6 was lost from the mammalian genome, and replaced by the rh gene much later.
B
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Compare the molecular formula of a carbohydrate (CH2O)n with that of carbon dioxide (CO2). What does the presence of hydrogen atoms in carbohydrates indicate?
A) Carbohydrates are more reduced than carbon dioxide. B) Carbohydrates are more oxidized than carbon dioxide. C) Every carbon atom in a carbohydrate is bonded to four different atoms. D) Carbohydrates contain a carbonyl functional group.
Which of the following is found in RNA but not in DNA?
A. Adenine B. Ribose C. Thymine D. Uracil E. Ribose AND Uracil
The primary function of erythrocytes is to participate in immune reactions
Indicate whether the statement is true or false.
The protozoan that causes malaria is an intracellular parasite of red blood cells (RBCs). An adaptive immune response to this parasite is problematic because
A) red blood cells do not produce MHC and, therefore, do not display the fact that they have been infected by presenting antigen. B) the parasite damages leukocytes along with RBCs. C) RBCs normally produce cytokines necessary for adaptive immune response, which this infection prevents. D) complement cannot effectively destroy RBCs. E) RBCs never enter lymphoid tissue.