170 ■ CHAPTER 09 What Genes Are
(^7) Select the correct terms:
To work on removing PERV DNA from the pig genome, researchers
first replicate the DNA many times, using (PCR / CRISPR). This
process increases the amount of DNA so that they are able to run
experiments to edit the genome, using (PCR / CRISPR).
Challenge Yourself
(^8) If a strand of DNA has the sequence CGGTATATC, then the
complementary strand of DNA has the sequence
(a) AT TCGCGCA.
(b) GCCCGCGCT.
(c) GCCATATAG.
(d) TA ACGCGCT.
(^9) Place the following steps of DNA replication and repair in the
correct order by numbering them from 1 to 5.
a. A template strand begins to be replicated.
b. If the incorrect base is not identified and replaced, it
remains as a point mutation in the DNA.
c. DNA polymerase identifies and replaces most incorrect
bases with the correct base, complementary to the base on
the template strand.
d. An incorrect base is added to the growing strand of DNA.
e. Proteins identify and replace any incorrect bases missed
by DNA polymerase.
(^10) Given the template DNA sequence GCAGCATGTT, identify each
of the following mutations to the complementary strand as an
insertion (I), a deletion (D), or a substitution (S).
a. CGTCGTACA
b. CGTGGTACAA
c. CGTCGTACTAA
(^11) If the target sequence for PCR on one strand of DNA is
ATGCAAATCCTGG, what is the sequence of each of the two strands
of the double-stranded DNA produced?
Tr y Something New
(^12) Using base-pairing rules to guide you, for a DNA double helix
that contains 20 percent adenine (A), specify the percentage of
(a) thymine, T; (b) guanine, G; and (c) cytosine, C.
(^13) Why do scientists need to use CRISPR to remove PERVs from
pig embryos, rather than just editing the genes in the organs of
adult pigs?
(^14) Scientists estimate that genes encoding proteins make up
less than 1.5 percent of the human genome. Other genes in our
cells encode different types of nonprotein RNA molecules. The
rest of our genome consists of various types of noncoding DNA,
defined as DNA that does not code for any kind of functional RNA.
Some of the remaining DNA has regulatory functions—for example,