Segments of polypeptides that are retained following protein splicing are called
A) introns.
B) exons.
C) inteins.
D) exteins.
E) cleavage products.
Answer: D
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Which of the following is the most likely explanation for the band pattern seen in lane 6?
A. Protein D is a restriction enzyme and cut the DNA fragment into two DNA fragments. B. Protein D binding to the CRP-binding site is less tight compared to cAMP-CRP binding. C. Protein D has a smaller mass than the cAMP-CRP protein. D. Protein D removed radioactive label from the DNA fragment.
Following are taxonomic categories matched with a common name of animals. Which of these is incorrectly matched?
A. Dipnoi/lungfish B. Actinopterygii/ray-finned fish C. Gymnophiona/caecilians D. Lepidosauria/lizards and snakes E. Therapoda/crocodiles
About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very
interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.) Refer to the paragraph about the formation of the Isthmus of Panama. The sister populations on opposite sides of the isthmus are true species under which species concept? A. the phylogenetic species concept B. both the morphological species and phylogenetic species concepts C. the morphological species concept D. the biological species concept E. the morpholoogical species, biological species, and phylogenetic species concepts
Under the microscope, you observe the first few cell divisions of an embryo. Instead of dividing the entire ball, the divisions are only separating the top half into smaller and smaller spheres. The bottom half appears to remain as one large cell. What is a likely explanation?
A. Gastrulation has occurred. B. A developmental error has occurred. C. The bottom half is the notochord. D. It is a bird or fish embryo.