Scientists estimate that over
10,000 disease are carried by genes to the offspring. Currently
about 4000 genes disorders have been identified amongst the
24,000 genes in humans but there are still thousands yet to be
discovered. This is why it is important to consider the life of
the, yet to be born, infant and check that the chance of passing
on of any adverse condition is reduced as far as is possible.
A normal human being has 22 pairs of autosomes and a sex
chromosome pair which determines the gender of the foetus making
46 chromosomes in all.
The egg or ova has an X chromosome and the sperm provides the X
or Y chromosome.
+ Y produces a male foetus and X + X produces a female foetus.
One example of a genetic disorder is Down's Syndrome where there
can be three of the autosome 21 instead of two known as Trisomy
or where this 21st chromosome fails to separate during egg or
Carrier screening can find out
if there is a currently known genetic abnormalities, that the
mother to be or her partner has, that may be passed on to the
foetus. It is important to have this test if a hereditary
condition exists in the family of either partner. Knowingly
passing on any condition that could have been prevented is
Test are easily done by blood or
saliva and can save a possible lifetime of disability for the
child and, in some cases, early mortality.
If one parent to be is a carrier
of a defective gene for a recessive disorder that means they
have one normal copy of the gene from one of their parents and
one defective copy from the other. Carriers don't usually have
any symptoms of the actual disease. The option, if this is the
case, is to have artificial insemination using a donor egg or
sperm or in vitro fertilization, which allows for genetic
testing of the embryo before it's implanted.
Unfortunately, the genes
responsible for many rare genetic diseases have not yet been
discovered. If this is the case, and a condition exists within
the family, it would be safer to have artificial insemination
using donor eggs or sperm or not conceive at all. Adoption is
also, obviously, a safer option.
In the UK it was been passed that babies can now be created with DNA from two women and one man. The technique uses a modified version of IVF to combine the DNA of the two parents with the healthy mitochondria of a donor woman. It results in babies with 0.1% of their DNA from the second woman and is a permanent change that would be passed down through the generations.
It is very important to
make sure the mother-to-be is in full health well before
conception as this will also affect the health of the foetus in
its vital early development stage. Drugs, alcohol, smoking
tobacco and any mineral or vitamin deficiencies will have a far
reaching adverse effect on the child’s lifetime both physically
SOME HEREDITARY DISEASES
There are over 4000
currently known gene carried disorders and more are being discovered
all the time. Most are, as yet, incurable which is why it is so
important to make sure defective genes are not passed on. This is a
partial list of hereditary conditions and diseases.