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Mutated blood cells occur in
sickle-cell disease—a genetic disorder
passed on when both parents carry
the faulty gene. It can be painful and
increases the risk of serious infections.of disorders caused by gene
mutations include cystic fibrosis
and sickle-cell disease.
Although many mutations are
harmful, occasionally a mutation
will confer an advantage on an
individual, enabling it to survive in
its environment better than others
of the same species. This type of
mutation may end up being passed
on through the process of natural
selection. Over many generations,
mutation is a mechanism for
diversification, survival of the
fittest, and ultimately evolution.The human genome
On April 14, 2003, scientists
completed the lengthy task of
mapping (sequencing) the entire
human genome. Geneticists worked
out the precise position of all the
base pairs in a chain of some three
billion of the base nucleotides
comprising an estimated 30,000
individual genes. This has allowed
geneticists to identify new genes
and the role they play in organisms.
Armed with this knowledge,
an individual can find out if they
have inherited a faulty gene from aTHE STORY OF EVOLUTION
parent. Additionally, with access
to such data it is possible to
screen embryos for known genetic
disorders before implantation in the
womb. By March 2018, the DNA of
around 15,000 organisms had been
sequenced. Such information can
help show how animals are related
in the evolutionary line and how
they have diversified.
While the discovery of the
composition and structure of DNA
has revolutionized the science of
heredity, it is worth noting that
the regions of DNA used for coding
proteins account for just 2 percent
of the entire human genome.
The nature of the other 98 percent
is not yet fully understood by
geneticists, but it is believed that at
least some of these regions involve
the regulation of the way genes are
expressed, or activated. It seems
that many more discoveries await
future geneticists. ■DNA barcoding
The idea of DNA barcoding
was first raised in 2003 when
a team at the University of
Guelph, Canada, suggested
that it would be possible to
identify species by analyzing
a common section of their
DNA. Led by Dr. Paul Hebert,
researchers chose a region in
the gene known as cytochrome
c oxidase 1 (“CO1”), made up
of 648 base pairs. This region
is quick to analyze, but the
sequence is still long enough
to differentiate between and
within animal species.
Different gene segments can
be used for other forms of life.
The first part of the
barcoding system involves
cataloguing samples of known
species. The DNA is extracted
and organized into a sequence
of base pairs, a process known
as “sequencing.” The sequence
is then stored in a computer
database, so that when a DNA
sample from an unknown
species is sequenced and
entered into the database, the
computer will match it with
existing records. The barcoding
technique has proved useful
for taxonomy, helping classify
animals and plants.With genetic
engineering, we will
be able ... to improve
the human race.
Stephen HawkingUS_034-037_The_role_of_DNA.indd 37 17/12/2018 14:33