Scientific American - February 2019

February 2019, ScientificAmerican.com 35

CGGG AAGGGGGG GGG AAAGGG AGGGAGGGGGGCCCCC AAGGG AGGGGGGGGGGGGGG AGGG A GGGA GGGA

AGGGGGGCC A

AAAAAAAA C CCCC C CC TTTTTGGGGGGGGGGGG

GGGATTT

TTTTTTTT TTT

CACGGGATTTTTT

TTT TTT

TTTAGGGTTT

TTT

AAA TTTCGGGGGGGGGGGCTTTAGG

GGGAGGGGGGCC AAAATTTCGGGGGGGGGGGGCTTTAGGGTTTCACGGGATTTTTT CCTTTGGGATTTGGG

TTT TTT TTT TTTTTT TTT TTT

GGGAATTT

CACGGGAATTTTTT

GGGGGGGGGGGG GGG

GGG

GGGGGG

AAAAAA AA

AA

AA AA

C C

CC

TTT TTT

TTT TTT

Illustration by Rebecca Konte

Road to Resurrection

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(^1) From dried plant samples,
researchers extract tiny
DNA fragments.
(^2) The fragments are analyzed
in a sequencer machine,
which reads the order of their
component nucleotides
(dubbed A, T, C and G).
 The gene that researchers
want to re-create is for
sesquiterpene synthase (SQS),
the enzyme that assembles
®¹åàD ̈åy ́﮹ ̈yù ̈yåÎ
Scientists take the ancient
åyÕùy ́`yåD ́mŠ ́må¹®y
that match par ts of an SQS
sequence based on a gene in
a current organism. The living
sequence becomes a template
to determine the position of
each fragment.
 The reconstructed sequence
is turned into real DNA with
a DNA printer, which builds out
the molecule one component
at a time. The end product is
an SQS gene.
 The gene is inserted into
a yeast “host” engineered
to accept it, and the yeast
colonies grow in small wells.
The instructions coded into
the SQS gene tell the yeast
to make a scent molecule,
just as they once instruc ted
the ancient hibiscus.
DNA fragments Sequencer
Template SQS gene drawn from related organism
Template sequence helps
to determine which DNA
fragments go nex t to one
another and if some nucleo-
tides are mismatched.
DNA printer
Printed SQS gene
Gene
transferred
to yeast
Ye a s t c e ll
Nucleus
Dried
Hibiscadelphus
wilderianus specimen
Scent molecule
Missing sections
between fragments
DàyŠ ̈ ̈ymĀŸï›
sequences from
Reconstructed mountain the template.
hibiscus SQS gene
Mismatch
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