Palytoxin is incredibly toxic, perhaps the second most dangerous nonpeptide toxin. It targets the sodium-potassium pump, locking it open and forming a channel through which the ions can passively flow. Palytoxin is produced by zoanthid cnidarians (soft coral), and there have been incidents of poisoning from zoanthids within marine aquaria tanks in people's homes. It is also thought to be the source of the legend of the Limu make o hana ("Seaweed of Death from Hana").A Hawaiian legend tells of a village that angered a shark god. In revenge, a "seaweed" began to grow in the tidepools that killed anyone who touched it. In fact, this "limu - make - o - Hana" - a zoanthid cnidarian - contains a palytoxin that locks the sodium-potassium pump open, allowing free flow of ions. If a villager
suffers palytoxin poisoning, which way will the ions in his neurons flow?
A. All ions will flow out
B. Chloride and sodium out, potassium in
C. Sodium in, potassium out
D. Potassium in, sodium out
Answer: C
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A. fluorescence microscopy B. standard light microscopy C. confocal microscopy D. differential-interference light microscopy E. transmission electron microscopy
Which of the following substances is secreted by an endocrine gland?
a. Tears b. Breast milk c. Wax d. Saliva e. Hormones
During meiosis, pairs of homologous chromosomes line up at the metaphase plate where they attach to kinetochore microtubules and are drawn to opposite poles of the cell. The selection of chromosomes from each pair is essentially random and accounts for much of the immense variety of traits displayed by sexually reproductive organisms, as illustrated in this diagram. Despite a similar division of genetic material between daughter cells in mitosis, no shuffling of chromosomes occurs. What accounts for this difference between meiosis and mitosis?
a. During mitosis, only a single combination of chromosomes is possible due to a slight polar charge that is absent during meiosis.
b. During mitosis, only a single combination of chromosomes is possible due to enzymes that arrange chromosomes in order.
c. During mitosis, only a single combination of chromosomes is possible because no recombination occurs and the homologs are never separated.
d. During mitosis, only a single combination of chromosomes is possible because nonconforming cells trigger an immune response.
A pair of chromosomes that contain alleles for the same genes at the same locations are
A. haploid. B. homologous. C. homozygous. D. synapsed.