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Table 1 Relative fitness of worm genotypes (per generation) as a function of host genotype

From: Adaptation of gastrointestinal nematode parasites to host genotype: single locus simulation models

Worm genotype

Sheep genotype

Susceptible (aa)

Heterozygous (Aa)

Resistant (AA)

 

frequency

(1-x) 2

2x(1-x)

x 2

Wild-type (bb)

(1-p) 2

1

1 - ¼s h

1 - ½s h

Heterozygous (Bb)

2p(1-p)

1 - ½s p

1 - ½s p

1 - ½s p

Alternate (BB)

p 2

1 - s p

(1+¼s h )(1-s p )

(1+½s h )(1-s p )

  1. s h = survival advantage of the alternate B allele for worms when harboured by sheep carrying the ‘resistance’ A allele; s p = survival trade-off (mortality) for the B allele, independent of sheep genotype.
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Genetics Selection Evolution

ISSN: 1297-9686