Chapter 20 Questions

In recombinant DNA experiments, what is used to cut pieces of DNA and what joins the resulting fragments to form recombinant DNA?

a restriction enzyme ... DNA ligase Restriction enzymes cut DNA molecules at specific points; in most cases, the restriction fragments have sticky ends that can base-pair with complementary sticky ends. The joined segments are then covalently fused by DNA ligase.

Why is it so important to be able to amplify DNA fragments when studying genes?

A gene may represent only a millionth of the cell's DNA.

Pax-6 is a gene that is involved in eye formation in many invertebrates, such as Drosophila. Pax-6 is also found in vertebrates. A Pax-6 gene from a mouse can be expressed in a fly and the protein (PAX-6) leads to a compound fly eye. This information suggests which of the following?

Pax-6 is highly conserved and shows shared evolutionary ancestry.

A researcher is using adult stem cells and comparing them to other adult cells from the same tissue. Which of the following is a likely finding?

The cells from the two sources exhibit different patterns of DNA methylation.

Which of the following is true of stem cells?

Their use is highly controversial. They can differentiate to produce many different kinds of specialized cells. They can be found in both embryonic and adult tissues. They can reproduce indefinitely in culture. All of the above.

Archaeologists unearthed a human skull with a small dried fragment of the scalp still attached. They extracted a tiny amount of DNA from the scalp tissue. How could they obtain sufficient DNA for an analysis of the ancient human's genes?

Use the polymerase chain reaction. PCR is a method of DNA amplification.

Yeast cells are frequently used as hosts for cloning because they _____.

are eukaryotic cells

To introduce a particular piece of DNA into an animal cell, such as that of a mouse, you would most likely be successful with which of the following methods?

electroporation followed by recombination

Gel electrophoresis separates DNA fragments on the basis of what characteristic?

length As the DNA fragments move through the gel, longer fragments are impeded more than shorter fragments, producing characteristic banded patterns in the gel.

Which of the following is most like the formation of identical twins?

organismal cloning

A paleontologist has recovered a bit of tissue from the 400-year-old preserved skin of an extinct dodo (a bird). To compare a specific region of the DNA from the sample with DNA from living birds, which of the following would be most useful for increasing the amount of dodo DNA available for testing?

polymerase chain reaction (PCR)

A gene that contains introns can be made shorter (but remain functional) for genetic engineering purposes by using _____.

reverse transcriptase to reconstruct the gene from its mRNA