Nerve-like muscle cells that function as the heart's pacemaker are found in the:
A) sinoatrial node.
B) coronary arteries.
C) left ventricle.
D) right ventricle.
E) atrioventricular valves.
Answer: A
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Which of the following syndromes has a karyotype with a missing X chromosome?
A. Jacobs syndrome B. Turner syndrome C. Williams syndrome D. Klinefelter syndrome E. Down syndrome
In his monohybrid crosses, Mendel deduced that one trait was recessive because that trait was ____
a. not present in the F1 and did not reappear in the F2 b. present in the F1 and in the F2 c. not present in the F1 and reappeared in the F2 d. present only in the parents e. present only in the F2
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.
Rickettsias are ________ intracellular bacteria.
Fill in the blank(s) with the appropriate word(s).