Xeroderma pigmentosum is a human genetic disease caused by
A) elevated levels of cholesterol in the blood.
B) failure to produce pigment that protects the skin cells from UV light exposure.
C) defective DNA excision-repair mechanisms.
D) mutations that inactivate tumor suppressor genes.
E) loss of genes controlling the SOS response.
C
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An ABC transporter:a
is a type of water channel. b. uses the energy of ATP to transport solutes. c. uses gated channels to transport ADP. d. is present in kidney tubules and prevents dehydration. e. is a type of porin.
Which of the following types of plants would not yet have been evolved in the forests that became coal deposits?
A) horsetails B) lycophytes C) pine trees D) tree ferns E) whisk ferns
When the environment is equal in solute concentration to the cell's internal environment then there is no net change in cell volume. This indicates a(n) ____________ solution around the cell.
A) hypotonic B) hypertonic C) isotonic D) barometric
Effects of bacterial exposure may lead to disease in the host. Place the following occurrences in the proper sequence or order.
A) disease, infection, contact B) contact, disease, infection C) contact, infection, disease D) infection, contact, disease