Download Gene Interaction Epistasis

Gene Interaction
Types of Gene Interaction
• Definition: coordinated action of non-allelic
genes controlling a single phenotypic trait
• Type 1: simple unmodified Mendelian
ratios
• Type 2: epistasis: modified Mendelian
rations
• Type 3 Quantitative “polygenic” continuous
variation (height)
Epistasis
• Definition: non-reciprocal interaction of non-allelic
genes so that one gene masks the phenotypic
expression of another non-allelic gene (opposite:
pleiotropy)
• Example Labrador Retrievers (E and B gene)
EE/Ee
BB/Bb
• Dilute golden -> brown -> black pigment
• E_B_ = black
• E_bb = brown
• eeB_ = golden
• eebb = golden Altered ratio: 9:3:4
• Genotype ee is epistatic (standing above or masking
remaining steps) to B_
• Geneotype B_ is hypostatic to ee
http://www.steve.gb.com/images/science/recessive_epistasis.png
Plumage in Parakeets
(genes A and B)
Gene A
Blue + yellow
White -> Yellow (gene B)
Gene B
White ->
Blue (with
gene A)
Parakeets
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If A is present and no B -> blue
If B is present and no A -> yellow
If B and A is present -> green
Neither (aa and bb) -> white pigment
• Precursor is white for both A and B
In horses
http://courses.bio.psu.edu/fall2005/biol110/tutorials/tutorial5_files/figure_14_11.gif
Mice
http://www.zo.utexas.edu/faculty/sjasper/images/14.11.gif
Kernel Anatomy
http://www.fao.org/DOCREP/W0073e/p255.gif
Pathways
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Colorless 1 -> (gene A1catalyzes)-> colorless 2
Gene A 2 catalyzes to bronze pigment
Gene Bz1 catalyzes to red pigment
Gene Bz2 catalyzes to purple pigment
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Gene C and R must be present to active pathway
Gene CI inhibits action of A1 = 13:1 ratio
Gene rr inhibits A1 =9:7 ratio
Gene bz1 bz1 inhibits Bz2 = 9:3:4
Gene a2a2 inhibits phenotypic expression of gene Y
(yellow endosperm) 12:3:1