Biology Now, 2e

Pigs to the Rescue ■ 167

Human stem cells are

obtained from the

transplant patient.

The guide RNA finds the target^3

DNA sequence through

complementary base-pairing, and

Cas9 cuts both strands of DNA in

the fertilized pig egg.

1

2 Deletion of the
kidney development
gene results in a pig
embryo that is not
able to grow kidneys.

(^5) The pig embryo
containing human
stem cells is inserted
into the uterus of a
surrogate pig.
7 The pig with human
kidneys is born.
9 The transplant patient
does not reject the
kidney, because it
grew from the
patient’s own stem
cells.
4 The stem cells are
inserted into the
pig embryo.
Stem cells
Pig embryo
without kidney
development gene
Gene controlling
kidney development
Guide RNA
Guide RNA
Cas9
6 Within the growing
pig fetus, the
kidneys develop
from the transplant
patient’s stem cells.
8 A human kidney is
removed from the
pig and transplanted
into the patient.
Figure 9.12
Human organs could grow up in pigs
Growing a human organ (here, a kidney) in pigs
modified by CRISPR to lack that organ could help
meet transplant needs.
Q1: Name a step in this process that is
similar to the original CRISPR method that
removed the PERVs from the pig genome.
(Hint: Review Figure 9.6.)
Q2: Name a step in this process that is not
included in the original CRISPR method that
removed the PERVs from the pig genome.
Q3: What parts of this process would
scientists need to change in order to
develop several different human organs in a
single pig?