Topic 1.9
In vitro fertilisation 2
IVF and stem cells
Aims
This activity extends the IVF sections of the course, and leads on from Topics 1.8 In vitro fertilisation
1 and 1.9 In vitro fertilisation 2. This activity describes IVF as a source of stem cells. Students will
become more aware of the current public issues and medical opportunities of embryonic stem cell
research. They should get practice and develop skills in making and defending a case using scientific
evidence. They should also recognise where science cannot provide further support and other methods,
such as the opinions of voters, are sought. Questions 3 and 4 recall the AS Human Biology passages on
cystic fibrosis and immune self-recognition.
Teacher notes
The questions are not in any particular sequence, and teachers may wish to use them singly or
in sub-sets. As far as possible, credit should be given for logical responses that use biological
facts from the student book and from the worksheet.
Answers to questions
1 Mr and Mrs Anderson are potentially fertile, but Mrs Anderson has a condition of the uterus that
has caused repeated spontaneous abortion (also known as a miscarriage). Through a respectable
agency, they arrange for an IVF embryo of theirs to be implanted in the uterus of a healthy young
woman, Miss Beach. When the baby is born, Miss Beach wants to keep it, and she rejects payment.
Mr and Mrs Anderson sue for custody of the baby. Who do you think is ‘really’ the mother? Whose
rights are greater? Consider genetics, risks and expenditures, physiological and emotional factors in
your answer.
Reference could be made to these considerations: Mr and Mrs Anderson and their family
have a unique genetic relationship to the baby; Miss Beach offers no such background, and
may remove the child from any contact with it. Miss Beach has undergone the risks, the
fatigue and the physical ‘wear and tear’ of pregnancy; however Miss Beach has been offered
payment for this; refusal of payment does not nullify any contract Miss Beach has signed.
Miss Beach probably has a stronger emotional bond with the baby when it is born; reference
may be made to maternal bonding and hormonal influence. The effect on the infant of an
ongoing dispute might be discussed as well as the two custody outcomes.
2 Adult bone marrow and embryos both contain stem cells. Which offer greater promise for treating
degenerative brain conditions like Parkinson’s disease? Explain your answer?
Embryo cells; because they are ‘totipotent’ whereas marrow cells normally differentiate only
into blood cells and platelets. Give credit for pointing out that patient’s own cells cause no
immune challenge and also for picking up the note in the worksheet background that more
ways are becoming possible of making adult cells totipotent.
AQA Human Biology A2 Stretch and challenge Teacher Notes © Nelson Thornes Ltd 2009
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Topic 1.9
In vitro fertilisation 2
3 Cystic fibrosis may be treatable using stem cells.
a) Considering the lung symptoms of cystic fibrosis, what tissues would need to be infiltrated with
new cells?
Airway-lining epithelial tissue.
b) What problems would arise in using
i) the patient’s own bone marrow stem cells?
Patient’s own cells carry the defective allele.
ii) stem cells from an embryo?
Embryo cells are non-self.
4 Techniques are being refined that could turn a clinically extracted cell from a child or adult into a
totipotent stem cell and then into a cloned human embryo.
a) How might this be useful to medicine?
The morula or later embryo could be harvested for stem cells to culture and use.
b) What problem in particular would it overcome when tackling diseases like Alzheimer’s with
embryo stem cells?
It would overcome the problem of rejection by the immune system of cells from a non-self
embryo.
5 The law needs a workable definition of when human life begins. Three ideas for this include: at
birth; when a fetus is old enough to survive in an incubator; or when the egg is fertilised (in or out
of the body). Which would be the easiest to defend scientifically? Which might be most practical
for a society which uses stem cell therapies? Give your reasons, and suggest another definition if
you wish.
The simplest to defend scientifically is the moment of union between sperm and ovum nuclei:
a new, separate life is thereafter viable in a healthy human reproductive tract. Credit for
noting that as techniques improve, the fetal age for survival outside (in incubators etc.) will
get lower. Embryonic stem cell research would be handicapped if human rights were enforced
for young embryos. Students should have the confidence to state that science has little more to
add to public debate about when life begins. This is one of the ‘boundaries’ mentioned in the
aims section of the worksheet.
AQA Human Biology A2 Stretch and challenge Teacher Notes © Nelson Thornes Ltd 2009
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Topic 1.9
In vitro fertilisation 2
6 IVF commonly produces several viable embryos. IVF embryos appear to have a higher incidence of
congenital defects (30% higher is a recent estimate). The embryos are subjected to testing before
implantation. Those that show up as possibly containing congenital defects are not used. Usually
some healthy embryos from the procedure also go unused. What should be the legal status of
unused embryos? Should they have a different status to a fetus facing abortion after being found to
have a serious congenital defect?
Credit should be given to those who pick up the point, from both the student book and the
worksheet background, that viable fertilised eggs are lost naturally. Also to those who add the
fact that young embryos are sometimes naturally aborted. Discussion may note that this is
often because they are defective; if the body naturally rejects defective embryos, then fetuses
found by artificial means to be defective could be deemed to have a lower status than healthy
ones. However no modern legal system applies such discrimination to disabled children once
born. (Another point for Question 5?) Further marks could be given to those who follow the
lead in the worksheet and point out that, artificially, many of the cells lost from tissues like
gut endothelium might soon have the potential to become embryos, albeit clones. The idea
might be reached that, since for such embryos to develop into a fetus they would (at present)
have to be implanted in a human uterus, that intervention further reduces their status to the
almost-synthetic, legitimate for destruction. If that is admitted, does it affect the status of
implanted IVF embryos? Perhaps credit should also be given for asking whether an IVF
embryo ought to have higher legal status if implanted in the uterus of the woman whose own
ovum was used, rather than a surrogate like Miss Beach.
7 Whose permission should be required before spare embryos are cultured for stem cells? Should
sick people who could be helped have a voice? Try to justify any suggestions logically.
Most students might say the parents’ but the stored embryos will not be in their keeping and
may still be in store after their contact with the IVF clinic has ceased. Permission in advance
could be mentioned. Give credit for raising the question of ownership between parents who
have, or have not, paid for IVF treatment. Most legal systems require persons doing embryo
research to have some sort of official permission. Patients have to signify consent to medical
procedures, if competent to do so. Credit should be awarded for any person or agency
nominated, if supported by a sensible reason but it should be pointed out in marking or
debrief that the more consents that are required, the more the delay and expense.
8 Describe a method used to detect congenital defects in a developing fetus.
It is suggested that the teacher directs which method the students are to describe, but it would
probably be amniocentesis or chorionic villus sampling, perhaps coelocentesis. Description of
how the karyotype is obtained and analysed should be sought, so ultrasound would not be
appropriate. Alternatively, students could be asked to compare the merits of two methods.
9 If a fetus is healthy but the pregnancy is not wanted, abortion can be induced. The legal codes of
different countries do not give the same rights to the parents and the fetus. Many people would give
greater rights to the fetus after it is old enough to survive outside the uterus. What do you think?
Use scientific points to back up your point of view.
It might help students to approach this question from a starting point of extremes, e.g.
prohibition of all abortion unless the mother’s life is imperilled; or free abortion on demand.
Some obvious dangers could be noted, then progress begun towards a more detailed answer.
Give credit for showing that age of survivability outside the uterus is a number slowly falling
as support for premature babies advances. Also for noting that the availability and quality of
such care varies from place to place. Credit medical and technical examples showing that
individual situations vary too widely for any simple law to be beyond criticism.
AQA Human Biology A2 Stretch and challenge Teacher Notes © Nelson Thornes Ltd 2009
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