Sometimes the tumor cells up-regulate the expression of anti-apoptotic proteins like BCL-2.

TLS Online TPP Program

#Id: 9189

#Section 3: Genetics, Cellular and Molecular Biology

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: 9190

#Section 3: Genetics, Cellular and Molecular Biology

Artificial selection- Genetically improving animals and plants by breeding together the best individuals in their fields and flocks.

TLS Online TPP Program

#Id: 9191

#Section 3: Genetics, Cellular and Molecular Biology

Types of selection

TLS Online TPP Program

#Id: 9192

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 9193

#Section 3: Genetics, Cellular and Molecular Biology

The allelic frequency at equilibrium (qˆ) depends on the relative fitnesses (usually expressed as selection coefficients) of the two homozygotes:

TLS Online TPP Program

#Id: 9194

#Section 3: Genetics, Cellular and Molecular Biology

Hitchhiking

An important consequence of linkage disequilibrium is hitchhiking. This happens when an allele at  one locus spreads by natural selection acting on a second locus that is in linkage disequilibrium with  the first.