#Question id: 15168
#Unit 2. Cellular Organization
#Question id: 5002
#Unit 11. Evolution and Behavior
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 above, which explanation is most likely?
#Question id: 1353
#Unit 4. Cell Communication and Cell Signaling
If a laboratory mouse had a mutation rendering the gene that codes for the L-selectin protein nonfunctional, which of the following symptoms would the animal exhibit?
#Question id: 2452
#Unit 2. Cellular Organization
Intermediate filaments
a. are typically 6 nm in diameter.
b. are essential for cell motility.
c. may be used to diagnose the tissue of origin for many cancers.
d. are composed of globular subunits.
e. are formed from tetrameric subunits.
#Question id: 961
#Unit 1. Molecules and their Interaction Relevant to Biology
Which type of organisms can eliminate excess nitrogen by the direct excretion of ammonia?