Atomic radii: The atomic radii of an atom depends on its position in the periodic table.

We can never determine the atomic radius of an atom because there is never a zero probability of finding an electron, and thus never a distinct boundary to the atom.

All that we can measure is the distance between two nuclei (internuclear distance).

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Duplicate gene and its parental copy can subfunctionalize so that each carries out only some of the roles that the ancestral gene performed. 

Ex- a duplicate of the β-hemoglobin locus is expressed in the fetus. 

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#Section 3: Genetics, Cellular and Molecular Biology

The loci that encode hemoglobins are members of a gene family, which is a set of loci that arose by duplication.

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#Section 3: Genetics, Cellular and Molecular Biology

Molecular Variation (Rate) - Which is the number of substitutions taking place per nucleotide site per year

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Nucleotide changes, particularly those at the third position of the codon, that do not alter the amino acid sequence are called synonymous substitutions.

Nucleotide changes in a gene that alter the amino acid sequence of a protein are referred to as non-synonymous substitutions.

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#Section 3: Genetics, Cellular and Molecular Biology

Most protein-encoding genes, the synonymous rate of change is considerably higher than the nonsynonymous rate because synonymous mutations are tolerated by natural selection

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Nonsynonymous mutations, on the other hand, alter the amino acid sequence of the protein and in many cases are detrimental to the fitness of the organism, so most of these mutations are eliminated by natural selection.