Do all living things die? Are there any immortal species? 70 (2/2) – Science Mysteries Explained

Q:
A:
life science
IDIOT’S GUIDES: SCIENCE MYSTERIES EXPLAINED
64
If we could control DNA, could we bring back any
extinct animal we wanted?
Since a complete DNA strand provides a full set of genetic instructions to make an an-
imal (or a plant), it must be theoretically possible to reconstruct extinct animals from
their DNA. But could we actually do it?
Current cloning technology can’t build an entire animal from a single strand of DNA, but the theory is
sound. If we figure out how to reliably insert DNA into “blank” cells, we can make extinct animals. But it
turns out DNA doesn’t last all that long ….
Think the instructions for flat-packed furniture are
complicated? They’re nothing compared to DNA.
With more than 400 million so-called nucleotides
providing instructions for how to assemble a spe-
cies, a DNA molecule is seriously big.
And any gap in the strand, even a tiny hole, will
make the strand useless. Extracting a complete,
undamaged strand of DNA from a long-dead animal
is incredibly dicult.
Movies and science fiction have suggested we
could use the DNA of a living animal to plug up
the gaps. The obvious example is to use African
elephant DNA to complete a strand of wooly mam-
moth DNA.
The problem with this, even if it did work,
might be philosophical rather than practical: is
the resulting animal a real mammoth—or is it
just a mutated African elephant with hair?
There’s an even bigger problem with using
DNA to resurrect ancient species. Chemically,
DNA is just a hydrocarbon, a gigantic molecule
made of hydrogen, nitrogen, carbon, oxygen, and
phosphorus. Compared to something like rock
or metal, it’s very unstable and delicate.
DNA breaks down by itself over time. Our
current models suggest that it completely de-
grades over about seven million years, though a
strand would become useless for cloning before
then.
That might seem like a long time, but if
seven million is the limit, that means we might
never be able to bring back dinosaurs—the last
dinosaur died around 65 million years ago.
LIFE SCIENCE
65
The most promising extinct candidates for DNA
recovery are animals that have gone extinct only recently.
High-profile examples include the Tasmanian tiger or
thylacine, a large marsupial that went extinct in 1935 at
an Australian zoo. There’s also the famous Dodo bird from
Mauritius, and the Yangtse River dolphin or baiji from
China.
These animals are good candidates because museums
have preserved specimens, and in the case of the thyla-
cine, that includes fetuses. There’s a better chance that
scientists could patch together a complete DNA strand
from these recent samples.
In fact, in 2008 scientists managed to inject a mouse
fetus with a gene from the thylacine responsible for form-
ing bone. It didn’t make the mouse look like a Tasmanian
tiger, but the research team was able to detect the gene
in the resulting mouse fetus. It’s a long way from a baby
thylacine, but it’s a start.
The important thing about DNA is the information
it carries—the instructions for building a life form—
rather than the actual molecule itself. Assuming we make
huge advances in biology and medicine, it’s theoretically
possible to build synthetic DNA from what’s called the
“genome”—a detailed description of DNA strand.
Genetic researchers analyze the DNA of living animals
to map—or “sequence”—their DNA. This information,
which adds up to about 3.2GB for a human, can be used to
figure out if a person is carrying the gene for, say, aggres-
sive breast cancer.
But it could also, theoretically, be used to clone the
person. Or the sheep. Or the wooly mammoth.
Today
Length of time on Earth
Millions of Years Ago
Herrerasaurus
Coelophysis
Allosaurus
Stegosaurus
Triceratops
Tyrannosaurus-rex
Oviraptorosaur
Oldest possible DNA
7 million years ago
Mesozoic Cenozoic
Triassic Jurassic Cretaceous Present
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