induced fit

Examples of induced fit in the following topics:

• Enzyme Active Site and Substrate Specificity

  • This model asserted that the enzyme and substrate fit together perfectly in one instantaneous step.
  • However, current research supports a more refined view called induced fit .
  • According to the induced fit model, both enzyme and substrate undergo dynamic conformational changes upon binding.

• Hybrid Zones

  • Over time, two species may further diverge or reconnect, depending on the fitness strength and the reproductive barriers of the hybrids.
  • Over time, the hybrid zone may change depending on the fitness strength and the reproductive barriers of the hybrids .
  • Hybrids can have less fitness, more fitness, or about the same fitness level as the purebred parents.
  • If the hybrids are as fit or more fit than the parents, or the reproductive barriers weaken, the two species may fuse back into one species (reconnection).
  • Discuss how the fitness of a hybrid will lead to changes in the hybrid zone over time

• The lac Operon: An Inducer Operon

  • The lac operon is an inducible operon that utilizes lactose as an energy source and is activated when glucose is low and lactose is present.
  • A major type of gene regulation that occurs in prokaryotic cells utilizes and occurs through inducible operons.
  • The lac operon is a typical inducible operon.
  • To do so, the cAMP–CAP protein complex serves as a positive regulator to induce transcription.

• Altruism and Populations

  • Behaviors that lower the fitness of the individual engaging in the behavior, but increase the fitness of another individual, are termed altruistic.
  • Thus, it is of fitness benefit for the worker to maintain the queen without having any direct chance of passing on its genes due to its sterility.
  • The lowering of individual fitness to enhance the reproductive fitness of a relative and, thus, one's inclusive fitness evolves through kin selection.
  • However, these behaviors may not be truly defined as altruism in these cases because the actor is actually increasing its own fitness either directly (through its own offspring) or indirectly (through the inclusive fitness it gains through relatives that share genes with it).
  • Both benefit from the interaction and their fitness is raised more than if neither cooperated or if one cooperated and the other did not.

• No Perfect Organism

  • Natural selection acts on the net effect of these alleles and corresponding fitness of the phenotype.
  • As a result, good alleles can be lost if they are carried by individuals that also have several overwhelmingly bad alleles; similarly, bad alleles can be kept if they are carried by individuals that have enough good alleles to result in an overall fitness benefit.
  • One morph may confer a higher fitness than another, but may not increase in frequency because the intermediate morph is detrimental.
  • The dark-colored mice may be more fit than the light-colored mice, and according to the principles of natural selection the frequency of light-colored mice is expected to decrease over time.
  • As a result, the frequency of a dark-colored mice would not increase because the intermediate morphs are less fit than either light-colored or dark-colored mice.

• Natural Selection and Adaptive Evolution

  • Natural selection acts at the level of the individual; it selects for individuals with greater contributions to the gene pool of the next generation, known as an organism's evolutionary fitness (or Darwinian fitness).
  • Fitness is often quantifiable and is measured by scientists in the field.
  • However, it is not the absolute fitness of an individual that counts, but rather how it compares to the other organisms in the population.
  • This concept, called relative fitness, allows researchers to determine which individuals are contributing additional offspring to the next generation and, thus, how the population might evolve.

• Reproductive Cloning

  • Reproductive cloning, possible through artificially-induced asexual reproduction, is a method used to make a clone of an entire organism.
  • Recent advances in biotechnology have made it possible to artificially induce asexual reproduction of mammals in the laboratory.

• Vestigial Structures

  • Vestigial structures have no function but may still be inherited to maintain fitness.
  • If there are no selection pressures actively lowering the fitness of the individual, the trait will persist in future generations unless the trait is eliminated through genetic drift or other random events.
  • This provides some selective pressure for the removal of parts that do not contribute to an organism's fitness, but a structure that is not directly harmful will take longer to be 'phased out' than one that is.

• Processes and Patterns of Evolution

  • Many mutations will have no effect on the fitness of the phenotype; these are called neutral mutations.
  • A mutation may affect the phenotype of the organism in a way that gives it reduced fitness (a lower likelihood of survival or fewer offspring).
  • A mutation may produce a phenotype with a beneficial effect on fitness.
  • Different mutations will have a range of effects on the fitness of an organism that expresses them in their phenotype, from a small effect to a great effect.
  • Scientists describe groups of organisms becoming adapted to their environment when a change in the range of genetic variation occurs over time that increases or maintains the "fitness" of the population to its environment.

• Cellular Differentiation

  • Mechanics of cellular differentiation can be controlled by growth factors which can induce cell division.
  • In asymetric cell division the cell will be induced to differentiate into a specialized cell and the growth factors will work in tandem.