Everyone is exposed regularly to ionizing radiation found in the soil, water, and air and from cosmic rays. In fact, 80% of the ionizing radiation people are exposed to comes from naturally occurring sources. Ionizing radiation can cause double-strand breaks in the DNA. Often, the DNA breaks have missing nucleotides at the broken ends. What type of repair would likely be used, and what would be the result of repairing this type of damage?
A. Direct repair would be used and would lead to properly repaired DNA.
B. Direct repair would be used to join the DNA, but errors would still remain.
C. Nonhomologous end joining would be used and would lead to properly repaired DNA.
D. Nonhomologous end joining would be used to join the DNA, but errors would still remain.
Ans: D. Nonhomologous end joining would be used to join the DNA, but errors would still remain.
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Freezing oocytes has not been as successful as freezing sperm because
A) they undergo an extra meiosis. B) the woman can become dangerously cold. C) ice crystals can form in the abundant, watery cytoplasm. D) the nuclei shatter.
During a particularly slow afternoon in the lab, you and your colleagues decide to play another round of Whose Heart Is This? The heart you are given has a pair of atria, but only a single, undivided ventricle. What type of animal did this heart belong to before it was given to you?
a. fish b. reptile c. amphibian d. mammal
__________ is one form of learning that happens only during a sensitive period early in life. Fill in the blank(s) with the appropriate word(s)
Which of the following statements about the classical pathway of complement activation is FALSE?
A) C1 is the first protein activated in the classical pathway. B) The C1 protein complex is initiated by antigen-antibody complexes. C) C3 is not involved in the classical pathway. D) Cleaved fragments of some of the proteins act to increase inflammation. E) C3b causes opsonization.