directional selection

(redirected from Positive selection)

directional selection

the SELECTION of a character in one direction, e.g. towards larger size, that may occur as a result in a change in environment. For example, if another ice age was imminent then temperature would fall and the overall size of warm-blooded vertebrates living in a particular region would probably increase. See BERGMANN'S RULE.
References in periodicals archive ?
Kyewski, "Antigen presentation in the thymus for positive selection and central tolerance induction," Nature Reviews Immunology, vol.
England captain Alastair Cook seemed delighted to have Steven Finn back to fitness and feels that positive selection headaches never hurt.
Specifically, DNA sequence data can construct phylogenetic (evolutionary) trees, identify subpopulations or genetic lineages, and examine the influence of horizontal gene transfer (in which an organism incorporates genetic material from another organism without being its offspring) and positive selection on the evolution of a given organism.
Positive selection was first performed with plasma from HIV-infected patients.
Recent genomic analysis of the Tibetan highlander population, that has been living at high altitude since 25000 years, has revealed that HIF-2 alpha, the oxygen sensitive subunit involved in the regulation of erythropoiesis, and genes related to the HIF signalling pathway, have been subjected to strong and recent positive selection (5), (6).
So, in these cases the recognizer for posture will mislead us to false positive selection posture instead of true positive grabbing posture.
All three players will be pushing for a return to the team after missing the victories over Scotland and Italy - leaving England's coaching staff with a positive selection headache.
That leaves Dalglish with a positive selection dilemma, and he admitted he can never imagine a situation at Anfield where his club is ripped apart like Carlos Tevez's situation at Manchester City this week.
These enrichment methods have also been combined, for example filtration devices with positive selection through an antibody against a pan-epithelial differentiation antigen, epithelial cell adhesion molecule (EpCAM), or ficol enrichment followed by positive immunomagnetic isolation.
"Today will be the first time this season I will have a positive selection headache.
KEY WORDS: Crassostrea, Crassostrea gigas, Crassostrea sikamea, Crassostrea angulata, fucose lectin repeats, sperm-egg interaction, positive selection
Detectors are generated via positive selection and negative selection in BIS.