74) How might stem cells be used to treat disease?

75) These days many of our food crops are genetically modified. To some people this “frankenfood” poses many dangers and should not be used. Do you agree? Why or why not?

76) A farmer wants to reduce his need to use insecticides on his corn crop to save money. He plants 80 percent of his field with Bt corn but has to plant the remaining 20 percent with corn that has not been genetically modified. What is the reason for planting only 80 percent of his field with Bt corn if planting 100 percent Bt corn would reduce his need for insecticide even further?

Refer to the figure below, and then answer the question that follows.

77) More than one restriction enzyme can be used to cut a piece of DNA at a time. If you used the restriction enzyme BamHI, which recognizes the sequence GGATCC (shown in the figure), as well as another enzyme that recognizes the sequence AATT, how many DNA fragments would be produced from the DNA strand shown?

A) two

B) three

C) four

D) five

Refer to the figure below, and then answer the question that follows.

78) In PCR, what is the function of the primers?

A) They separate DNA strands.

B) They are the starting point for DNA polymerase to work on synthesizing complementary DNA strands.

C) They tell DNA polymerase where to stop copying the template.

D) They are the source of nucleotides that DNA polymerase uses to copy the template.