Describe the steps in the polymerase chain reaction (PCR). What will be an ideal response?
ANSWER: 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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a. stratified b. dense connective c. loose connective d. simple e. more than one of these
This protein functions in muscle contraction.
a. Keratin b. Hemoglobin c. Actin d. Insulin e. Pepsin
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What will be an ideal response?
Which of the following is not true about the structure of DNA?
A. The bases form the "rungs" of the ladder structure. B. A always pairs with T and G always pairs with C. C. The sides of the ladder structure are made up of sugar and phosphate. D. The two strands are considered parallel. E. The ladder structure is twisted into a double helix.