Describe the steps in the polymerase chain reaction (PCR)
What will be an ideal response?
There are three steps in PCR. The first step is denaturation. A solution of DNA is heated to 90 to 100C for a few minutes to break the hydrogen bonds between the two polynucleotide strands, producing two single-stranded molecules that will serve as templates. The second step is hybridization. The DNA solution is rapidly cooled to about 50C, and primers for DNA replication bind to complementary regions on the single-stranded DNA fragments, marking the boundaries of the region to be copied. The third step is DNA synthesis. After the primers are bound to the template strands, the enzyme Taq polymerase (a DNA polymerase from a bacterial species found in hot springs) synthesizes a complementary DNA strand beginning at the primers.
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In the figure above, at which of the numbered regions would you expect to find cells at metaphase?
A) I and IV B) II only C) III only D) IV only E) V only
The purpose of irradiating foods is to
a. increase the vitamin content. b. increase the mineral content. c. destroy harmful bacteria, fungi and other microorganisms. d. limit spoilage. e. both destroy harmful bacteria, fungi, and other microorganisms and limit spoilage.
How long are most donated tissues able to be stored?
A) a week B) a month C) a year D) 5 years
Some complex viruses have icosahedral symmetry in the head region and helical symmetry in the tail. Overall, these viruses are said to have ________ symmetry.
A. radial B. binal C. complex D. bilateral