Neutral vs. Natural Selection

Module 7 - Molecular Evolution 

Neutral Selection vs. Natural Selection

Kimura argued that random "genetic drift" instead of natural selection is the main cause of evolution at the molecular level this is known as the theory of neutral evolution. Although initially, this theory was dependent on the cost of natural selection, it was later emphasized on the molecular clock which is the constancy of the rate of molecular evolution. The neutral theory also demonstrated the inverse relationship between the importance of a protein and its rate of evolution. Therefore, important proteins are more constrained and changes in their amino acids less likely to be neutral. Neutral drift is when non-synonymous and synonymous mutations are equal. Years later around the 1990s, DNA sequence data had increased leading to a comparison of patterns of substitutions. Nonsynonymous mutations are selectively important while synonymous mutation sites are selectively unimportant. [1]

Can you guess which mutations are influenced by neutral selection versus natural selection?

Neutral Selection 

An example of neutral mutations is how the human and bovine amino acid sequence differs but still performs the same function. [3]

Natural Selection 

According to the Handbook of Behavioral Neuroscience, Parkinsions Disease is an example of important site evolution. Variation in and around the LRRK2 gene has been associated with an increased PD risk. A variant arose due to nonsynonymous substitution called G2385R which is almost exclusively found in Asian populations and it's penetrance of the variant is modified by other PD risk factor associated loci polymorphisms such as MAPT and SNCA. [2]

Both natural selection and neutral selection cause changes in our DNA through mutations although neutral selection is known to occur more often in the molecular level.

Resources: 
[1] Neutral Selection 
[2] Natural Selection example 
{3] Neutral Selection example