The phrase "a variation that allows" is correct and usable in written English.
You can use it when discussing different forms or versions of something that provide a certain capability or permission.
Example: "We developed a variation that allows users to customize their experience based on their preferences."
Alternatives: "an option that enables" or "a modification that permits".
The twist in this tired scenario — a variation that allows Mr. LaBute, not for the first time, to assume the posture of social provocateur — is that Abel is not your average white bigot but rather a righteously angry, or at least seriously crazy, black one, played by (who else?) Samuel L. Jackson.
To deal with that issue, we replace the above constraint by a variation that allows the vertices to move closer.
If you're playing a variation that allows you to start with face up cards, choose cards in different columns.
In the animal-genetics lab, for example, the player visits a farm to sample meat, before learning how to develop a DNA test for double-muscled cattle (a genetic variation that allows animals to have more muscle fibre and less fat) and then playing detective to find out whether meats labelled as organic are abiding by the rules.
But it also has a strategy, called phase variation, that allows it to escape from attack by the human immune system.
If a population happens to have genetic variation that allows some individuals to survive a challenge better than others or reproduce more than others, then those individuals will have more offspring in the next generation, and the population will evolve.
The current molecular paradigm for neo-Darwinian evolutionary biology is that random DNA sequence mutations, gene flow, and genetic drift promote phenotype variation that allows an adaptation event to facilitate natural selection [ 1].
Only one VSG is expressed at a time with stochastic switching to provide antigenic variation that allows for evasion of the immune system.
Furthermore, many butterfly species show significant geographic variation that allows mapping and positional cloning of genes underlying natural pattern variation.
Natural selection, therefore, continually works to reduce genetic variation within populations, but populations risk extinction without the genetic variation that allows populations to respond evolutionarily to changes in the physical environment, diseases, predators, and competitors.
As the modes are defined through their topology, they combine class-invariant properties with within-class variation that allows for adjustments to specific task constraints.
