20
10
science news of the year | Genes & Cells
93 percent | portion of human dNA that a study suggests may be unnecessary
Single life source Statistical
analyses of protein structure
show that there is almost
no chance that present-day
life on Earth had more than
one common ancestor (SN:
6/5/10, p. 12).
count (chart below) puts the
figure at 22,333 (SN: 11/6/10,
p. 5).
The Adam sperm A gene
crucial for sperm production
arose just once, 600 million
years ago, and has governed
the genesis of male gametes
in animals ever since (SN:
8/14/10, p. 14).
Skin to neuron Using a new
technique, skin cells can be
converted directly into neurons without first reverting
to an embryonic state (SN:
2/27/10, p. 5).
Gene sequencing for
all, even Neandertals
An unprecedented picture of life’s diversity is emerging
as researchers publish the full genetic instruction books
of a growing list of species—including one that has
been extinct for more than 30,000 years.
A project sequencing Neandertal dNA harvested from
bones reveals evidence of prehistoric interbreeding
between humans and Neandertals (Sn: 6/5/10, p. 5). As
for modern humans, scientists have compiled complete
genetic profiles of Archbishop desmond tutu and a bushman tribal elder named !Gubi (Sn: 3/13/10, p. 16). full
genomes are also available for the first time for people of
African-American, mexican-American (Sn: 7/3/10, p. 13),
Japanese and irish descent.
in addition, the pilot phase of the 1000 Genomes project has unveiled millions of genetic variants in about 800
people of several different ethnic origins (Sn: 11/20/10,
p. 14). this snapshot reveals that the average person
carries defective copies of 250 to 300 genes, plus about
75 dNA variants associated with disease. similar
advances in dNA sequencing are also allowing researchers to decode the genomes of more species (see march
of genomes, page 29).
Now scientists are looking for ways to put all this
information to use. New techniques to read just the
protein-coding portions of genes, for example, show how
some mutations may contribute to mental retardation (Sn
Online: 11/14/10) and have revealed the genetic causes
behind some inherited diseases (Sn: 4/10/10, p. 12).
Vestigial no more Pseudo-genes, once thought to be
defunct copies of genes, still
have a purpose in life — to
regulate protein production
of their “functional” twins
(SN: 7/17/10, p. 14).
Walking bacteria Bacteria
can stand on end and stagger around, thanks to hairlike
appendages called pili (SN:
11/6/10, p. 8). The behavior
may be involved in exploring
new environments and could
help explain how antibiotic-resistant microbe communities called biofilms form.
Prions not all bad A study
in sea slugs suggests that
prions, the disease-causing
agents in mad cow disease,
may help form protective
sheaths around nerves (SN:
2/13/10, p. 17). A separate
study indicates proteins that
act like prions could be key
players in forming memories (SN: 2/27/10, p. 13).
DNA tagged for obesity
Chemical modifications to
DNA near genes involved
in weight regulation may
affect who becomes obese
and who stays lean (SN:
10/9/10, p. 15).
Gene count A decade after
completion of the Human
Genome Project, researchers still have not pinned
down the precise number of
protein-producing genes in
a human being, though one
Fruit ;y
14,889
Number of genes
Some modern humans have inherited a fraction of their
DNA from Neandertals (reconstruction, above right).
In;uenza
11
E. coli
4,149
Junk DNA A cross-species
comparison suggests that
more than 90 percent of
DNA in the human genome
has no known function (SN:
12/4/10, p. 17).
Grape
30,434
Human
22,333
Chicken
16,736
from top: ©Joe mcNAlly/recoNstructioN by keNNis ANd keNNis; t. dubÉ, cHickeN icoN: piNAre/sHutterstock,
HumAN icoN: mysoNtuNA/sHutterstock
