Mutations in the Pax6 gene cause developmental defects in the eyes of flies, mice, and humans. This suggests that:
A. the eyes of flies, mice, and humans
evolved by convergent evolution.
B. Pax6 may be a master regulator of eye
development.
C. Pax6 has been evolutionarily conserved.
D. Pax6 may be a master regulator of eye
development that has been evolutionarily
conserved.
E. Pax6 may be a master regulator of eye
development that has evolved independently
in the lineages leading to flies, mice, and
humans.
D
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Changes in temperature and pH can decrease an enzymes activity by breaking ________.
A. chemical bonds. B. covalent bonds. C. ionic bonds. D. hydrogen bonds. E. none of the above is correct.
The antibiotic rifamycin is selectively toxic in blocking protein synthesis in Mycobacterium tuberculosis because
A. the antibiotic binds to the mRNA once synthesized, preventing it from participating in the initiation complex with the ribosome. B. it binds preferentially to bacterial RNA polymerase rather than the eukaryotic protein, effectively halting transcription in the pathogen but not the host. C. bacterial ribosomes are 70s whereas host ribosome are 80s, thus the antibiotic binds to the M. tuberculosis ribosome but does not bind to the eukaryotic machinery. D. the drug binds to the initiator tRNA, preventing the formation of the protein synthesis initiation complex in the bacterial cell.
Migratory birds in the Northern Hemisphere most likely head to tropical overwintering grounds because ____
a. they are looking for appropriate sites for egg-laying b. of seasonal changes in the abundance of predators c. they are looking for appropriate breeding sites d. of seasonal changes in food supplies e. they are ectotherms and cannot withstand cold temperatures
Membership in a clade cannot be established by shared ancestral traits alone
_____________________ Indicate whether the statement is true or false.