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NEWSLETTER
September 19, 2016
Volume 11, Issue 3
Why the long neck?
Species: Okapi johnstoni and Giraffa camelopardalis
Genome size: 3.3 billion and 2.9 billion bases, respectively
The genomes of the only two extant members of the Giraffidae family—the okapi (Okapi johnstoni) and the giraffe
(subspecies Giraffa camelopardalis, tippelskirchi)—have been sequenced for the first time, according to a paper published
today (May 17) in Nature Communications. The sequences are likely to help explain the giraffe’s unique look.
“Through comparative analysis with other eutherians mammals, 70 genes were identified that exhibit multiple signs of
adaptation in giraffe,” the authors wrote in their paper. “Several of these genes encode well-known regulators of skeletal,
cardiovascular and neural development, and are likely to contribute to giraffe’s unique characteristics.”
By aligning the new sequences to known sequences in cattle (Bos taurus), the team of researchers from Tanzania, Kenya,
the U.K., and the U.S. came up with a list of 17,210 giraffe and 17,048 okapi genes. Comparing those sequences, the team
found that the giraffe’s long neck is likely a result of mutations in two sets of protein-coding genes—one controlling gene
expression patterns during limb development, the other controlling the expression of growth factors.
The researchers also linked a number of genes in giraffes to the evolution of a more powerful cardiovascular system to cope
with the strain of a longer neck. “Among mammals, giraffe has some of the most challenging physiological and structural
problems imposed by its towering height,” the authors wrote in their paper. “The solutions to these challenges, in particular
related to its turbocharged circulatory system, may be instructive for treatment of cardiovascular disease and hypertension in
humans.”
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