PCB 4674 Lecture Notes - Lecture 15: Allele Frequency, Standard Deviation, Coefficient Of Relationship

• School: FAU
• Department: Process Cell Biology
• Course: PCB 4674
• Professor: Theisen Timothy C.

Document Summary

Difference between the average value of the trait before selection and the average value of the trait after selection. When expressed in standard deviation units, it is called selection intensity. Equation for change in allele frequency between generations (delta q) delta q = [pq/w][w2-w1] *if delta q < 0: relative frequency of a2 decreases. *if delta q > 0: relative frequency of a2 increases. *if delta q = 0: it is bc of fixation or a stable polymorphism. Allele frequencies change fastest in the intermediate range because q = 1-p and delta q are quadratic functions of p (parabola). Dominance slows the rate of change when the deleterious (lower fitness) recessive allele is rare. When there are fitness differences among genotypes yet both alleles remain segregated in the population. There is no further change in the allele frequencies yet selection is still acting. Stable polymorphism can occur when: the heterozygote has the highest fitness and fitness is negatively frequency dependent.