Final answer:
The statement aligned with the neutral theory of molecular evolution is that the majority of mutations are neutral and do not affect an organism's fitness, with much of the genetic diversity in populations due to the random fixation of these mutations. Option 1 is the correct answer.
Step-by-step explanation:
The statement that is consistent with the neutral theory of molecular evolution is: 'Most mutations are neutral in their effects on the organisms in which they occur.' According to the neutral theory of molecular evolution, posited by Motoo Kimura, the majority of evolutionary changes at the molecular level are caused by genetic drift of mutationally neutral alleles that do not affect an organism's fitness. This theory posits that the genetic diversity in populations is mainly due to the random fixation of these mutations rather than adaptive selection.
Breaking down the provided statements:
- Most mutations are deleterious and are quickly eliminated from the population. - This does not correspond to the neutral theory, which suggests most mutations are neutral.
- The rate of molecular evolution is constant over time. - While this may sometimes be observed as a consequence, it is not a core principle of the theory.
- Natural selection is the primary driving force behind molecular evolution. - Neutral theory specifically indicates that much of the molecular evolution is independent of natural selection, driven instead by random drift.
- Genetic drift has no effect on the genetic variation within a population. - The neutral theory actually argues that genetic drift can have a significant effect on genetic variation.
The correct answer is 'Most mutations are neutral in their effects on the organisms in which they occur.'