GENES AND DNASCIENCEGenetic diseases Some genes
contain errors that cause them to
malfunction. These faulty genes can
cause diseases such as cystic fibrosis
and sickle cell anemia. Most disease
genes are “recessive,” like the gene for
blue eyes, meaning the disease only
develops if a child inherits a faulty
copy from both parents.
Cloning means using DNA from
an organism to create an identical
new individual, or clone. Some
clones occur naturally—many plants
and some simple animals reproduce
by cloning, and identical twins
are clones. Artificial cloning
can be used to grow new
organs for transplant
patients.u CHEMICAL CURE In the future,
GM crops should reduce the need to treat
fields and orchards with chemicals that
may harm the environment.GM crops Genes can be transferred
into plants to create transgenic, or
“genetically modified” (GM) crops.
GM technology has been used to
produce rice enriched with
vitamins, corn and cabbages that
produce their own insecticides,
and soybeans that survive being
treated with weedkillers that kill
all other plants.u GLOW FOR IT These mice were
given a jellyfish gene to make them glow
in the dark.Doctors use gene
therapy for the first
time, treating a four-
year old girl suffering
from an
immune disorder.The first
experimentally
cloned mammal,
Dolly the sheep,
is born.The completed sequence of
the human genome is
published.Marshall Nirenberg
deciphers the genetic
code hidden in the
order of the bases.Frederick
Sanger begins
sequencing
DNA.1961 1970 1990 1996 2003
TAKE A LOOK: GENOME
u CYSTIC FIBROSIS is caused by
a mutation in a gene controlling the
production of sweat and mucus.
FACT FILE
■ Scientists can “cut and paste” genes
from one species into another to create
useful characteristics. The genetically
altered organism is described as
“transgenic.” Transgenic bacteria are
used to produce useful drugs, and
transgenic mice are used to research
cures for many diseases.. DESIGNER
BABY
Would you pick
and choose which
genes to pass on to
your children?
■ A genome is the entire genetic code
inside an organism. The first genetic
code to be sequenced in full was that of
a virus known as bacteriophage phi
X174, in 1975. In 1984, the first
bacterial genome was sequenced, and in
1990 scientists began to sequence the
human genome. The project took 13
years to complete. They found that the
genes were padded out by sequences of
“junk DNA,” which had no obvious
function. The human genome contains
about three billion base pairs and codes
for roughly the same amount of data
that can be fit on one CD. u THE CHROMOSOMES in this
preparation have been treated to
make a particular gene glow green.