The gene for Tay-Sachs disease codes for a nonfunctional form of the enzyme hexosaminidase A (or Hex
A). It has been found that a person with only one-third the maximum amount of Hex A can function absolutely normally. Please characterize the heredity of Tay-Sachs disease.
A) codominant
B) recessive
C) dominant
D) multiple allelic
B
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Which of the following statements is true of the photosynthetic structures in bryophytes?
A. Thalloid and leafy species are found in all groups of bryophytes. B. A thallus is a thin stem that supports the leaves of bryophytes. C. Bryophytes have true leaves similar to those found in gymnosperms. D. All hornworts have leaf-like photosynthetic structures. E. All mosses have leaf-like photosynthetic structures.
The countercurrent exchange system found in fish gills maximizes gas exchange efficiency by:
a. producing rapid water flows across the gill surface. b. allowing water and blood to come in direct contact to maximize oxygen exchange. c. having a high concentration gradient of oxygen at the start of the capillaries. d. maintaining a high concentration gradient of oxygen along the entire length of capillaries. e. decreasing the oxygen content of the blood leaving the gill filaments
Chromosomes first become visible during
A. prophase I. B. metaphase I. C. anaphase I. D. telophase I.
Salmon are able to live in both fresh water and salt water. Salmon are therefore:
A. conformers. B. effectors. C. regulators. D. conditioned.