W09_Discussion_Disease2

W09_Discussion_Disease2 - 1 Monday evening • Morning...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 Monday evening • Morning SNAFU – Question (thanks to Alp) • Does balancing selection result necessarily in evolution? – Tail in of Natural Selection Lecture: lost slides. • We will do those. • Evening Session—Marquez and epidemics Heterozygote advantage & Heterozygote advantage & warfarin warfarin resistance resistance in Norway rats: the data please in Norway rats: the data please … 1.000 0.378 0.568 0.568 0.054 Observed Frequencies 1.000 0.437 0.448 0.448 0.115 H-W Expected Frequencies TOTAL W r W r W s W r W s W s Observed Observed f(W f(W s ) = 0.339 ) = 0.339 Observed Observed f(W f(W r ) = 0.661 ) = 0.661 Does Heterozygote Advantage lead to Does Heterozygote Advantage lead to shifting allele frequencies through time? shifting allele frequencies through time? Observed Observed f(W f(W s ) = 0.339 ) = 0.339 Observed Observed f(W f(W r ) = 0.661 ) = 0.661 1.000 Observed Frequencies 1.000 0.437 0.448 0.448 0.115 H-W Expected Frequencies TOTAL W r W r W s W r W s W s 1.000 Observed Frequencies 1.000 H-W Expected Frequencies TOTAL W r W r W s W r W s W s F2 F3 broadened unchanged Disruptive narrowed changed Directional narrowed unchanged Stabilizing Variance in trait value Mean Trait value TYPE OF SELECTION A word about mortality and natural selection Frequency Frequency-dependent selection in scale dependent selection in scale-eating cichlids eating cichlids Hori (1993) Science 260 : 216 Perissodus Perissodus microlepis microlepis Left Left-mouthed mouthed P. P. microlepis microlepis attack attack right flank of prey right flank of prey Right Right-mouthed mouthed P. P. microlepis microlepis attack attack left flank of prey left flank of prey Sample Year Sample Year Frequency left Frequency left-mouthed fish mouthed fish 2 Positive versus negative frequency dependence • Positive frequency dependence – The more common a particular trait, the more the trait is favored • Negative frequency dependence – The less common a particular trait, the more the trait is favored. Negative Frequency Dependent Selection Gamoetophytic Gamoetophytic self self-incompatibility genes incompatibility genes Almonds (and many, many other plants) Almonds (and many, many other plants) Rare advantage frequency dependence An agricultural problem • Gametophytic self-incompatibility allows individuals to avoid selfing and maintains high genetic variability.genetic variability....
View Full Document

This note was uploaded on 10/08/2009 for the course BIS 2 taught by Professor Schwartzandkeen during the Spring '09 term at UC Davis.

Page1 / 7

W09_Discussion_Disease2 - 1 Monday evening • Morning...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online