An x-linked gene produces spots on some platyfish. all platyfish have an autosomal repressor that inhibits the expression of the spot-producing gene. the closely related swordtail lacks both the spot-producing gene and the repressor. in backcrosses between these two species, some hybrids receive the spot-producing gene but not the repressor. these individuals can develop malignant tumors, because the expression of the spot-producing gene is not properly regulated. this appears to be an example

The correct answer is - The Dobzhansky-Muller Model.

Explanation:

The Dobzhansky- muller model is a model that explains about how the natural selection influences speciation or reproductive isolation in a specific process when hybridization takes place between 2 species of an organism.

The offspring that produce through this process is an incompatibility with other species of origin. In the given question, spotted platyfish that arise due to the X linked gene exhibits the Dobzhansky-muller model.

Thus, the correct answer is - The Dobzhansky-Muller Model.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.