1 Scientists have cloned sheep but have not yet cloned a human. The best explanation for this situation is that

(1) the technology to clone humans has not been explored
(2) human reproduction is very different from that of other mammals
(3) there are many ethical problems involved in cloning humans
(4) cloning humans would take too long

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2 The diagram below represents a process that occurs within a cell in the human pancreas.

This process is known as

(1) digestion by enzymes
(2) protein synthesis
(3) energy production
(4) replication of DNA

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3 When a personís teeth are being x rayed, other body parts of this person are covered with a protective lead blanket to prevent

(1) loss of hair
(2) increase in cell size
(3) changes in DNA molecules
(4) changes in glucose structure

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4 The diagrams below represent portions of the genes that code for wing structure in two organisms of the same species. Gene 1 was taken from the cells of a female with normal wings, and gene 2 was taken from the cells of a female with abnormal wings.

The abnormal wing structure was most likely due to

(1) an insertion         (3) a deletion
(2) a substitution      (4) normal replication

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5 During the warm temperatures of summer, the arctic fox produces enzymes that cause its fur to become reddish brown. During the cold temperatures of winter, these enzymes do not function. As a result, the fox has a white coat that blends into the snowy background. This change in fur color shows that

(1) the genes of a fox are made of unstable DNA
(2) mutations can be caused by temperature extremes
(3) random alteration of DNA can occur on certain chromosomes
(4) the expression of certain genes is affected by temperature

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