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Q: infertility ( Answered,   3 Comments )
Subject: infertility
Category: Science
Asked by: drader14-ga
List Price: $2.00
Posted: 10 Apr 2006 17:51 PDT
Expires: 10 May 2006 17:51 PDT
Question ID: 717594
If infertility is caused by genetic factors, are we increasing the
possibility of bringing children into the world with abnormalities by
developing techniques that allow infertile couples to have children?
Subject: Re: infertility
Answered By: alanna-ga on 28 Apr 2006 14:10 PDT
Hi drader14-ga

As the commentators report below,  where infertility is genetic, the
genes will be passed on to offspring who will carry  "infertility
genes,"  but may or may not be infertile themselves.

But often the egg or the sperm of an infertile couple are not used in
in-vitro vertilization; there is a donor for one or the other.  In
this case, the offspring will be free of "infertile genes," if there
are any.

However, It is likely that many if not most infertile people do not
have genetic infertility.  These genes would surely have died out--or
become very rare--during the course of our human evolution. Simply
put, infertile people did not reproduce before our modern age, so
genes making people infertile would have died out.

I am directing you to a website that shows the various causes of
infertility in males and females.

To take just a few examples from that site, excessive running or
chemotherapy or cannabis or advanced age use can cause hormonal
problems in women with infertility resulting.  These "conditions" are
all environmental, not genetic.

Thanks for using Google Answers.

All the best,

Subject: Re: infertility
From: davedamage-ga on 11 Apr 2006 04:27 PDT
If there were a genetic component to infertility (which i would not
doubt) then by using techniques to help people overcome these problems
and have children we would inevitably end up with a larger proportion
of the population having genetically-influenced fertility problems. If
we did not have techniques to help them then obviously their genes
(including those predisposing to reduced fertility) would not be
passed on.

The question of these children having 'abnormalities' is entirely
dependant on your definition. Children of people with (genetic)
fertility problems would be more likely to have (genetic) fertility
problems than children of parents without genetic fertility problems,
so if you were to consider that an abnormality then yes. Obviously,
however, children of parents with genetic fertility problems will be
no more likely to suffer from any other genetic 'abnormality' (however
you are defining that) e.g. Down's syndrome.

We must of course remember that there are many people who suffer
fertility problems for a wide variety of reasons: many are
environmental, and I would assume that more still will be due to a
combination of environmental and genetic factors. It is also
interesting to note that there is the possibilty that some genes could
have a detrimental effect on fertility in conjuction with one set of
environmental circumstances and could have no effect (or indeed a
positive effect) in other circumstances.

I cannot tell if your question is also relating solely to genetics or
to the effectiveness of the 'techniques' that are being used to
overcome fertility problems as well. If it is both then i'm afraid i
have no idea wether there are more likely to be mutations in genes if
fertilisation is carried out 'artificially'. Although it is an
interesting thought.

I'm sure only half of this answer is right, but that is my
understanding so far. If anyone can correct me - please do! Hope that
gives you a slightly better idea of the answer to your question.

Subject: Re: infertility
From: jytung-ga on 11 Apr 2006 08:51 PDT
The previous comment made a number of good points, but I'd like to add
a few things and clarify some others.

A number of papers published in peer-reviewed scientific journals have
shown that there is a genetic component to both male and female
infertility.  For example, 10-15% of men with azoospermia (no sperm in
the ejaculate) have a deletion of a gene on the Y chromosome called
the DAZ gene, that is, their Y chromosome is missing that gene.  For
women, twin studies have shown that the heritability for age at
menopause (early menopause is one type of female infertility) can be
as high as 63%, which basically says that your genes are likely to
play a high percentage role in your age at menopause.  Let me know if
you'd like some sample references.

Assisted reproductive techniques (ART) such as in vitro fertilization
(IVF) or intracytplasmic sperm injection (ICSI) allow couples with
various types of fertility problems conceive children.  As the
previous commenter pointed out, without these techniques, the genetic
problems that an infertile couple may possess would not be passed on
to any offspring.  In addition, it is also most likely true that the
interaction that a particular person's set of genes has with his or
her particular environment can influence the outcome, on fertility or
any other characteristic.  For instance, a fair-skinned individual may
be more susceptible to developing skin cancer than a darker-skinned
individual; however, if the fair-skinned person spends little to no
time in the sun, he will probably not develop skin cancer.  This
person's genes simply predispose him to a particular condition, but
his interaction with the environment is also key.

Getting back to assisted reproduction and genetic problems, one thing
that I feel I ought to clarify is that there is some evidence that
certain genetic problems that lead to infertility could also lead to
other genetic abnormalities.  Certainly, some genetic causes of
infertility, such as loss of the DAZ gene, only appear to affect
fertility and no other processes.  In that case, if a man is infertile
because of a DAZ deletion, and he and his partner undergo IVF to have
a child, any sons they produce will also have the same DAZ deletion
(since a father passes his Y chromosome to all of his sons) and will
likely be infertile themselves.  However, there is evidence that some
infertility in both men and women may be associated with
nondisjunction of the chromosomes or defective meiosis.  Both of these
processes have to do with the complicated dance of chromosomes that
must occur for proper sperm and egg formation.  In the case of
nondisjunction, a child may end up with an extra chromosome or an
extra part of a chromosome.  In most cases, this combination of
chromosomes is not compatible with life and the embryo is
spontaneously aborted, probably much before a woman would suspect that
she might be pregnant.  A few combinations of extra chromosomes are
compatible with viability, such as an extra chromsome 21 (Down's
Syndrome) or extra X or Y chromosomes.  So you can see that if a
couple is infertile because one of them is genetically predisposed to
have problems with chromosome nondisjunction, they may be more likely
to produce a child with an abnormal number of chromosomes.

In the case of problems with meiosis, many of the genes required for
this process are also important in the DNA repair processes that are
important for preventing cancer.  Your DNA is often damaged by things
in the environment--UV light, free radicals, chemical agents,
etc.--but your body has a system in place to find these broken bits in
your DNA and fix them.  It's really remarkably efficient, but genetic
defects in this machinery do happen and then broken bits can go
unrepaired.  Mistakes in certain important genes can lead to the
unrestrained cell growth and division that is the basis of cancer. 
Therefore, these defects can not only make you susceptibile to
infertility (through defective sperm or egg development), but also
potentially susceptible to cancer.

There was also one study that showed that babies born through assisted
reproductive techniques have a 2x higher incidence of certain birth
defects, but this isn't really very high and I don't know how
reproducible those results are.  Some scientists are concerned that
simply putting embryos through the process of coming out of the body,
sitting around in a petri dish and under microscopes can be damaging,
even though the techniques are constantly being improved.

But I don't mean in any way to be alarmist, or imply that because of
IVF, we're selfishly producing many children who are born with
disadvantages.  Most of the children born through ART are healthy and
I'm sure their parents couldn't be happier.  Besides, I don't know
whether the genetic problems that are associated with infertility are
any worse than those that aren't but certainly don't prevent people
from having children, such as susceptibility to diabetes,
hypertension, or high cholesterol.  I'm sure the possibility of
passing on genetic problems to their children is, however, a concern
for many potential parents, since everyone wants the best possible
lives for their family.  Many IVF clinics offer genetic counseling to
couples to let them know what the risk factors may be.  In addition,
techniques to test embryos for certain genetic defects, such as
preimplantation genetic diagnosis (PGD), are being developed to let
people know whether a couple has passed on a genetic defect (cystic
fibrosis, for instance) to a particular embryo.

Anyway, I hope this is somewhat useful at least.  I apologize if I've
been too jargon-y, just let me know.  There are a number of good
resources available on the web relating to ART and reproductive
medicine in general.  Try the American Society for Reproductive
Medicine's website--it should be reliable.
Subject: Re: infertility
From: kakulia-ga on 16 Apr 2006 07:16 PDT
The answer is a clear YES.

   In fact the same applies to several other genetically transmitted

   However,there is little that can be done,for people even when
alerted to the consequences persist with propagation, and since
marriages invariably are outside the immediate family , the defective
strains would only multiply and theoretically one day would permeate
the whole populace.

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