NEUTRAL THEORY OF MOLECULAR EVOLUTION PART B CSIR NET DEC 2017

The neutral theory of molecular evolution (proposed by MOTTO KIMURA) 1968 holds that at the molecular level most evolutionary changes and most of the variation within and between species is not caused by natural selection but by genetic drift of mutant alleles that are neutral.

SOME IMPORTANT POINTS -

• Except for advantageous mutations most alleles are under neutral condition.
• The rate of evolution for most genes will be equal to the neutral mutation rate .
• At the level of Dna sequences,genetic drift dominates evolution i,e genetic drift is the main force changing allele frequency .
• The rate of replacement in evolution resulting from the random genetic drift of effectively neutral mutations is equal to the mutation rate to such alleles, μ.
•  Explained the unexpectedly high rate of evolutionary change and very large amount of intraspecific variability at the molecular level that had been uncovered by new techniques in molecular biology. 
• A neutral mutation is one that does not affect an organism's ability to survive and reproduce. 
• The neutral theory allows for the possibility that most mutations are deleterious, but holds that because these are rapidly purged by natural selection, they do not make significant contributions to variation within and between species at the molecular level. 
• Mutations that are not deleterious are assumed to be mostly neutral rather than beneficial. 

CSIR NET  DEC 2017 PART B 

Which one of the following statements is NOT TRUE about the Neutral Theory as proposed by Motoo Kimura?

1.Except for advantageous mutations, most alleles are under neutral selection

2. The rate of evolution for most genes will be equal to the neutral mutation

rate

3. Advantageous mutations are exceedingly rare

4. At the level of DNA sequences, genetic drift dominates evolution

Answer-  3

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