CHAPTER 19
Concept check questions (in figure legends)
FIGURE 19.1
Concept check: How many hydrogen bonds are holding these two DNA fragments
together?
Answer: Eight
FI GURE 19.2
Concept check: Explain the role of the selectable marker gene in this experiment.
Answer: In this experiment, the selectable marker gene selects for the growth of bacteria
that have taken up a plasmid.
FI GURE 19.3
Concept check: Explain the meaning of the name “reverse transcriptase”.
Answer: Reverse transcriptase refers to the idea that this enzyme catalyzes the opposite
of transcription. It uses an RNA template to make DNA, whereas during transcription a
DNA template is used to make RNA.
FI GURE 19.5
Concept check: After 4 cycles of PCR, which type of PCR product predominates?
Explain why?
Answer: The products that predominate are the DNA fragments that are flanked by
primers. This occurs because these products can be used as templates to make products
only like themselves.
FI GURE 19.7
Concept check: What needs to happen so the reporter molecule can emit fluorescence that
is not quenched?
Answer: The probe must be cleaved to separate the quencher from the reporter.
FI GURE 19.9
Concept check: What is an advantage of making a cDNA library rather than a
genomic library?
Answer: The advantage of a DNA library is that it lacks introns. This is useful if a
researcher wants to focus their attention on the coding sequence of a gene or if they want
to express the gene in cells that do not splice out introns.
FI GURE 19.11
Concept check: What type of information is obtained under conditions of low stringency?
Answer: Conditions of low stringency reveal gene families.
FI GURE 19.13
Concept check: What is the purpose of using a secondary antibody?
Answer: The secondary antibody is labeled, which provides a way to detect the protein of
interest.
FI GURE 19.15
Concept check: How does the binding of a protein to DNA influence the ability of DNase
I to cleave the DNA?
Answer: The binding of a protein to DNA prevents DNase I from cleaving the region
where the protein is bound.
FI GURE 19.18
Concept check: Describe three possible uses of site-directed mutagenesis.
Answer: Some examples are: to study the core promoter of a gene; to study regulatory
elements; to identify splice sites; and to study the importance of particular amino acids
with regard to protein function.