An enormous tree's enormous genome, genes for strong-swimming sperm and more presented May 7-11 in Cold Spring Harbor, N.Y.
An enormous tree's enormous genome, genes for strong-swimming sperm and more presented May 7-11 in Cold Spring Harbor, N.Y.
By Tina Hesman Saey
Web edition: May 16, 2013
BIG GENOME
Loblolly pine trees (shown) are used for lumber, paper and many other products. Scientists have compiled the organism?s genome, the largest ever attempted.
Credit: National Park Service (NPS); U.S. Department of the Interior
A record-setting genome for a towering giant
Deciphering the genome of the loblolly pine is a tall order, as is perhaps fitting for a tree that can grow to be 30 meters in height.
Researchers sequenced the conifer?s (Pinus taeda) approximately 24 billion bases of DNA, Steven Salzberg of Johns Hopkins University reported May 10. That surpasses the previous record holder, wheat, by more than 7 billion bases. The DNA is distributed over 12 chromosomes, each about two-thirds the size of the entire human genome.
A preliminary analysis suggests the trees may have up to 64,000 protein-coding genes, although Salzberg says the number is probably smaller. Humans have just over 22,000 protein-coding genes.
Next, the researchers will tackle the sugar pine genome. That one is even bigger, with more than 35 billion DNA bases.
Strong swimming sperm?s secret
A gene variant can make sperm strong and speedy, a study of wild mice suggests.
Researchers compared two species of wild mice -- one promiscuous, one monogamous -- to learn how genetic factors produce physical characteristics that may give one species an evolutionary edge.
By pitting sperm from the two species against each other in a race to the top of a test tube, Hopi Hoekstra, a Harvard University evolutionary geneticist, and her group found that the fastest sperm are ones that have tails with a longer midsection. Hoekstra reported May 9 that the team traced the genetic source of that structural difference to a variant in the PRKAR1A gene. In people, male infertility can accompany mutations in that gene.
The gene?s activity is higher in hybrid males carrying at least one copy of the promiscuous species? version than in males with two copies the monogamous version. And males with the promiscuous gene produce sperm with longer midsections and appear to have a mating advantage even when no other males are around. Of the males that sired pups when left alone with a female for a week, 45 percent carried two copies of the promiscuous species? version of the gene, while only 25 percent had two copies of the monogamous species? version.
In and out of Africa
Migration out of Africa wasn?t a one-way journey, a new study suggests. In about 1,000 BC, a large group of people made the reverse trek from the Middle East into eastern Africa, evolutionary geneticist Joseph Pickrell of Harvard Medical School reported May 11.
Those migrants mixed with east Africans, and their descendants carried their genetic heritage into southern Africa.
Pickrell and his colleagues discovered the back-to-Africa migration while investigating a genetic connection between Italians and some southern Africans. Shared genetic variants between southern Europeans and Africans could mean that factions of the original Middle Eastern population migrated both into Africa and into Europe.
Citations
P. de Jong et al. The sequencing, assembly, and characterization of a 24Gb conifer genome (P. taeda). Presentation at the Biology of Genomes meeting, May 10, 2013.
H. Hoekstra. The genetics of adaptation in wild mice. Presentation at the Biology of Genomes meeting, May 9, 2013.
J. Pickrell et al. Unraveling waves of population mixture in sub-Saharan Africa using patterns of linkage disequilibrium. Presentation at the Biology of Genomes meeting, May 11, 2013.
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