“My little brother was born to save my life.”
- Charlie Whitaker, 2005
In 2004, Jamie Whitaker became Britain’s first “designer baby”. He was selected as an embryo to be
the perfect tissue match for his older brother, Charlie. Charlie was born with a rare blood disorder
that was expected to kill him before the age of 30. His only hope was a stem cell transplant from a
matched donor. Sadly, no donor was found. Desperate, Charlie’s parents travelled to the United
States to go through preimplantation tissue typing, a technique that at the time was illegal in the
United Kingdom, to ensure that their next child was the perfect match. They succeeded. A year after
receiving a stem cell transplant from his baby brother’s umbilical cord blood, Charlie was given the
“all-clear” by his doctors. Before the transplant Charlie required blood transfusions every three
weeks and almost nightly 12-hour drug infusions, just to keep him alive.
Genetic advances have great potential for improving our health. However, they also raise a great
number of questions around privacy, access to information, and commodification of life.
Preimplantation tissue typing is one of a number of genetic tests that can be used to gather
information about an embryo prior to its birth. Genetic tests are often used to detect mutations in an
embryo or fetus that are linked to a particular condition. Several different types of genetic tests can
occur before birth (Figure 16.1).
Prenatal genetic screening
Prenatal genetic screening is usually offered to parents who are at high risk of having a child with a
recognizable genetic condition. A limited number of diseases can be detected this way, including
Down’s syndrome, sickle cell anemia and cystic fibrosis. The tests are done, once a woman has
conceived, through a blood test. Further testing can be done through a technique called
amniocentesis. Amniocentesis is usually done between the 14th and the 17th week of pregnancy.
During the procedure, a thin needle is guided through using an ultrasound into the woman’s uterus,
and a sample of amniotic fluid is retrieved. Amniotic fluid surrounds the fetus inside the mother, and
contains fetal cells in it. The fetal cells can be analyzed for genetic abnormalities. If the fetus is
affected by a genetic disease, the couple is usually faced with the decision of whether to terminate or
continue the pregnancy. In Canada, prenatal genetic screening is offered free of charge.
Preimplantation genetic diagnosis
Preimplantation genetic diagnosis and preimplantation tissue typing are both techniques that can be
used to screen embryos that are created through in vitro fertilization, so-called “test tube babies”.
During in vitro fertilization eggs from the female are joined with sperm from the male in a Petri plate,
and the resulting embryos begin to divide under artificial conditions (Figure 16.2). Once the embryos
are at the eight-cell stage, a single cell is removed and tested. The testing, in the case of genetic
diagnosis, is usually done for the presence of particular genetic mutations. This way couples where
one or both carry disease-causing mutations can select the unaffected embryos for implantation.
Preimplantation genetic diagnosis can test for over 50 genetic conditions. It has been used
extensively by high-risk individuals to conceive babies that are free of particular mutations. For
example, a woman with a family history of breast cancer can use this technique to select an embryo
that is free of the mutation. Doing the testing prior to implantation avoids having to make a decision
whether to terminate or continue a pregnancy when the embryo is known to carry an undesirable
mutation.
Preimplantation genetic diagnosis also allows for sex selection if there are underlying genderassociated medical conditions. For example, some diseases, such as Duchenne muscular dystrophy,
are well known to affect males more than females. Therefore, if the parents know that they are
carriers for the disease, it may be medically preferable to select the child’s gender so that the disease
is not passed on. In Canada, non-medical sex selection is illegal.
Preimplantation tissue typing
Preimplantation tissue typing is an extension of preimplantation genetic diagnosis. Here, once again,
the embryo is tested prior to implantation. This time the testing is done to “match” the tissue of an
existing, sick child, in order to create a “savior sibling”. Using the results of the test, parents and
doctors select the embryo for implantation that has the same tissue type as the sick child. As in the
case of Charlie Whitaker, when the donor child is born the stem cells from its umbilical cord can be
used to treat the sick sibling.
This particular application of prenatal testing has raised the most concern over “spare part” babies.
Some groups have expressed concerns over the long-term psychological welfare of a child who was
created for the purpose of “donation”. The child may feel objectified, as a means to an end, rather
than an end itself. Others argue that children born through this procedure are loved and supported by
their parents just like any other children. If anything, they argue, a child that is the result of such a
difficult and very much premeditated decision is likely to be very much cherished.
As of September 2010, Canada did not have clear rules regarding preimplantation tissue typing.
How Much Do You Want to Know? [major]
In May 2010 an over-the-counter genetic test was about to be released into drug stores across the
United States. The genetic test was going to be used to determine the customers’ genetic propensity
for a range of conditions. The test contained a small saliva collection kit, and a postage-paid
envelope that customers could use to send their saliva sample back to the laboratory of the kit’s
manufacturer, Pathway Genomics. Once the saliva had been sent the customer could simply visit the
company’s website and order their own, individualized genetic report. You could choose to have a
pre-pregnancy analysis to identify disease characteristics that could potentially be passed to your
children. You could choose to generate a medication responsiveness profile to determine which
drugs may be helpful or harmful to you. You could also learn if you might have an increased chance
of developing a range of medical conditions: cancers, diabetes, obesity, heart disease, Alzheimer’s,
etc.
The very week that the kit was to be made available, the Food and Drug Administration (FDA) halted
its distribution. Why did the FDA step in? The issue of the implications of wide spread genetic
testing was, and still is, a controversial one.
Genetic test: how they work [minor]
Genetic tests, or DNA-based tests, are a direct result of the human genome project. They involve a
direct examination of the DNA molecule, in order to determine if an individual’s genetic material
shows a predisposition to inherited diseases.
DNA tests are used in medicine for a range of reasons. For example, the adult daughter of a mother
who had early-onset breast cancer may choose to be tested to determine if she carries one of the
mutations associated with breast cancer. An individual coming from a family affected by
Alzheimer’s disease may choose to have testing to estimate the risk of developing the disease.
Someone with a family history of Tay-Sachs disease, a severe metabolic disorder, may choose to
have a carrier screening test to determine if he or she can pass the gene for the disease to a child. In
other cases a DNA test can be used to confirm a suspected diagnosis
Regardless of the reason for the test, DNA testing allows for a diagnosis of the vulnerability, or
likelihood, of developing an inheritable disease. Several hundreds of conditions can be tested for,
and more tests are being developed. Genetic tests can be done on a variety of tissues, but most
commonly they are done on a blood or saliva sample. Once collected, the sample is sent to a
laboratory where laboratory technicians will analyze it for DNA or chromosomal changes, depending
on the tests being done.
As you already know, with the exception of single-gene disorders, most diseases can be attributed to
several genes. Furthermore, the environment can also influence the expression of a particular trait.
Consequently, the results of genetic tests are not always straightforward. They can be challenging to
interpret and explain, requiring specialized healthcare professionals and extensive counseling of the
clients. For example, a positive result for an increased risk of developing cancer does not predict the
course or the severity of the disease. It can only be used to indicate a likelihood of the disease, but is
not in itself a diagnosis. The result is a prediction, and as such cannot be used to establish the exact
risks of developing a particular disorder.
Often, genetic testing forces the client to make other, difficult decisions. Since family members have
at least some genetic material in common, a positive test for a particular inherited condition may have
implications for the blood relatives of the person undergoing the testing. Hence, the client needs to
decide whether he or she will inform the relatives of the results of the test or not.
On the other hand, having a negative test may not give any useful information. Many variations of
genes do not affect health. In the case where a genetic test finds a difference in DNA that is not
known to cause a disease it can be difficult to tell if the difference is a disease-causing mutation or a
natural, non-threatening variation. Furthermore, just like a positive genetic test, in the absence of
symptoms, cannot be used to establish the exact risks of developing a disease, neither can a negative
test. Many tests cannot detect all the possible genetic changes that are associated with a particular
disease.
Ethical, legal, and social issues [minor]
Although the physical risks associated with most DNA tests are very small, the outcome of the testing
can have far-reaching consequences. Most of the risks associated with genetic testing involve social,
financial, and emotional consequences.
Since the results of DNA tests may apply to blood relatives, genetic testing can create tension within
a family. At the same time, the information the tests provide is limited and can’t determine, with
certainty, whether or how a disease will progress. Lack of treatment for some of the detectable
disorders can further compound anxiety and frustration felt by individuals and families involved in
testing.
The issue of privacy and access to personal genetic information also raises many questions. Since a
predictive test can be used to show whether someone is at higher risk of developing a particular
condition, the information could, potentially, be of interest to a variety of parties. There is concern
that genetic predispositions towards certain diseases could be used to deny health insurance to
individuals. Employers may also be interested in knowing the probabilities of their workers
developing chronic conditions. The possibility of genetic discrimination is a definite concern. From
a research point of view access to an individual’s genomic information combined with medical
history and lifestyle information could make a great difference in understanding the genetic basis of
disease.
In the United States, in order to prevent genetic discrimination, the Genetic Information
Nondiscrimination Act was introduced in 2008. The act prohibits group health plans and insurers
from denying coverage or charging higher premiums based on genetic predisposition. It also
prevents employers from making job placement decisions based on an individual’s genetic
information. It is hoped that the act will facilitate the advancement of personalized medicine. In
Canada, there are no existing legal documents specifically prohibiting genetic discrimination,
although the Canadian Charter of Rights and Freedoms guarantees equality to all people.