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lecture 8. Epistasis and Pathways. Interactions of null alleles Additivity of nulls implies distinct pathways. Epistasis of nulls implies common pathway. Synergism of null alleles implies parallel pathways with a common target. Additivity of hypomorphs is consistent with anything. 1. 3.
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Interactions of null alleles Additivity of nulls implies distinct pathways Epistasis of nulls implies common pathway Synergism of null alleles implies parallel pathways with a common target Additivity of hypomorphs is consistent with anything
1 3 Y X Z 1 2 Z X Y 1 2 3 X Y Z
Switch Regulation Pathway outcome 1 A B condition outcome 2 Yes ON ON outcome 1 outcome 2 No OFF OFF
Switch Regulation Pathway outcome 1 A B condition outcome 2 Yes OFF ON outcome 1 outcome 2 No ON OFF
Some C. elegans sexual specializations Male tail sensory structures that locate the vulval opening spicules Hermaphrodite vulva 2° 1°: the opening vulval muscle-1 insertion cues to male 2°: vulval muscle-2 insertion cues to male 1°
somatic sex determination in C. elegans • genotype XX XO • +fm • tra-1(lf)m m • tra-1(gf)ff • her-1(lf) ff • her-1(gf)~m m • f, female somatic tissues; • m, male somatic tissues. • lf, loss-of-function; • gf, gain-of-function
somatic sex determination in C. elegans • genotype XX XO • +fm • tra-1(lf)m m • tra-1(gf)ff • her-1(lf) ff • her-1(gf)~m m • tra-1(lf); her-1(lf)m m • tra-1(gf); her-1(gf)ff
OFF ON ON OFF
Intragenic revertant of a dominant mutagen • egl-1(sd)+ +ced-9(gf) • egl-1(sd) + + ced-9(gf) • egl-1(sd) ced-9(gf) • + + • egl-1(sd) ced-9(gf+lf) • + + x Common Non-Egl OR Rare Egl In egl-1(sd) mutants, the HSN dies, and hence the hemaphrodites cannot lay eggs
ced-3(lf) NO cell death ced-4(lf) NO cell death ced-1(lf), 2, etc No engulfment ced-9(gf) NO cell death ced-9(gf+lf) EXTRA cell death nuc-1 No DNA degradation ced-3(lf) ced-9(lf) NO cell death ced-3 (lf) nuc-1(lf) NO cell death