Overdominance the heterozygote has higher fitness than the  fitnesses of the two homozygotes

Underdominance, in which the heterozygote has lower fitness than both homozygotes.

Directional selection leads to fixation of the favored allele and elimination of the other allele, as  long as no other evolutionary forces act on the population.

TLS Online TPP Program

#Id: 8963

#Section 3: Genetics, Cellular and Molecular Biology

If the duplicate is redundant and does not provide a fitness benefit, it will be lost by deletion or the accumulation of loss of-function mutations.

A second fate is that a duplicate can simply retain its original function.

TLS Online TPP Program

#Id: 8964

#Section 3: Genetics, Cellular and Molecular Biology

A third fate that can befall a duplicated gene is neofunctionalization. Here the duplicate evolves a novel biological function. 

TLS Online TPP Program

#Id: 8960

#Section 3: Genetics, Cellular and Molecular Biology

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. 

TLS Online TPP Program

#Id: 2243

#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.

TLS Online TPP Program

#Id: 8966

#Section 3: Genetics, Cellular and Molecular Biology

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

TLS Online TPP Program

#Id: 2234

#Section 3: Genetics, Cellular and Molecular Biology

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.