Molecular Genetics

A human genome is composed of somewhat more than 3 billion pairs of DNA bases. Any two randomly selected humans will share 99.9% of their DNA sequence; we are genetically quite similar to one another. Nonetheless, 0.1% of 3 billion gives 3 million genetic differences; there are also many genetic differences among us. Molecular genetics seeks to identify the genetic variants that contribute to individual differences in a specific trait. Molecular genetic approaches are often contrasted with biometric approaches. The latter is focused on quantifying the overall contribution of genetic factors (e.g., estimating heritability), whereas the former aims to identify the specific variants that contribute to heritability.

A genetic variant refers to a population difference in the DNA sequence (i.e., the G, C, T, and A ...