Heterosis Hybrid Vigor q An increase in the

Heterosis (Hybrid Vigor) q An increase in the performance of hybrids over that of pure breeds, most notieceably in traits like fertility survivability.

Heterosis (Hybrid Vigor) q I. Positive Heterosis q II. Negative Heterosis q Measuring hybrid vigor q Retained hybrid vigor

Measuring Hybrid Vigor q In practice, hybrid vigor is measured as difference between the average performance of crossbreds and the average performance of their purebred parent lines or breeds.

Hybrid Vigor q Utilization of heterosis in broiler and laying hen production q Utilization of heterosis in beef production q Utilization of heterosis in lamb production

GENE FREQUENCY IN POPULATIONS AND POPULATION GENETICS Genetic Equilibrium A population in the absence of forces that change gene and genotypic frequencies A gene frequency : p a gene frequency : q p + q = 1

GENE FREQUENCY IN POPULATIONS AND POPULATION GENETICS A population: Ø in the absence of forces that change gene and genotypic frequencies Ø presence of random mating Males: A and a genes: p. A and qa Females: A and a genes: p. A and qa

GENE FREQUENCY IN POPULATIONS AND POPULATION GENETICS Genotype Frequencies Ovum p. A qa Spermatozoon p. A qa p 2 AA pq Aa q 2 aa p 2 AA+2 pq. Aa+q 2 aa=1 Hardy-Weinberg Equilibrium

GENE FREQUENCY IN POPULATIONS AND POPULATION GENETICS Deviations from Hardy–Weinberg equilibrium q Genetic Drift q MUTATION q MIGRATION q SELECTION q RANDOM DRIFT