The last common ancestor of all bilaterians is thought to have had four Hox genes. Most extant cnidarians have two Hox genes, except Nematostella (of ?-catenin fame), which has three Hox genes. On the basis of these observations, some have proposed that the ancestral cnidarians were originally bilateral and, in stages, lost Hox genes from their genomes. If true, this would mean that _____.
A) the Radiata should be a true clade
B) the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral trait
C) Hox genes play little actual role in coding for an animal's "body plan"
D) the Cnidaria may someday replace porifera as the basal bilaterians
B) the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral
Answer: B) the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral trait
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The region of the large intestine that when stretched stimulates the defecation reflex and allows for the passage of feces.
A) Large intestine B) Stomach C) Esophageal cancer D) Appendix E) Mouth F) Salivary glands G) Rectum H) Cirrhosis I) Gallbladder J) Small intestine
Four of the five answers listed below are related by a similar gland. Select the exception
a. goiter b. deficiency of iodine in the diet c. hypothyroidism d. rickets e. excessive stimulation of the thyroid gland
Which of the following would you find in a Sanger sequencing reaction but not in a polymerase chain reaction?
A) DNA template B) DNA polymerase C) dNTPs D) ddNTPs E) DNA primer
Which of the following statements about what we have learned by comparing the modern-day human genome to other genomes is true?
(a) Modern humans whose ancestors come from Europe or Asia share up to 4 percent of their genome with Neanderthals. (b) Accelerated changes, which were found when comparing the human genome to other mammalian genomes, were not found when comparing the modern-day human genome to the Neanderthal genome. (c) The human genome is far more gene-dense than the yeast genome. (d) In syntenic regions of the human and mouse genomes, both gene order and the placements of more than 95% of the mobile genetic elements are conserved.