P F 1 CCpp X ccpp Cp Cp CcPp X CcPp F 2 CP Cp cp cp CP Cp cp cp CCPP CCPp CcPP CcPp CCPp CCpp CcPp Ccpp CcPP CcPp ccpp ccpp Summary: 9/16 purple, 7/16 white CcPp Ccpp ccpp ccpp
AABB X aabb P AB ab Gametes AaBb X AaBb F 1 x F 1 AB Ab ab ab AB Ab ab Yellow Yellow ab Yellow Green Where A--- is white, aab- is yellow, and aabb is green.
AABB Genotypes Interactions AABb AaBB AaBb AAbb Aabb aabb aabb aabb Epistasis Dominance Phenotypic Classes Example Phenotypes (Classical Complete 9 3 3 1 Garden peas 9 yellow round ratio) for A,B seed color 3 yellow and surface wrinkled texture 3 green round 1 green wrinkled None Complete X-X- 3 0? 1 Guinea pig 3 short yellow for A, -X-? hair length (X) incomplete - and color 6 short cream for B - (-) 3 short white 1 long yellow (0) 2 long cream (?) 1 long white 66
AABB AABb AaBB AaBb AAbb Aabb aabb aabb Epistasis Dominance Phenotypic Classes Example Phenotypes aa epistatic Complete 9 3 4 Mice coat pattern 9 agouti to B,b for A,B and color or 3 colored (Recessive) Labrador 4 white retriever color A epistatic Complete 12 3 1 Summer squash 12 white to B,b for A,B fruit color or 3 yellow (Dominant) Foxglove color 1 green A epistatic Complete 13 3 1 Chicken color 13 white to B,b; bb for A,B 3 colored epistatic to A,a (Dominant and Recessive) aa epistatic Complete 9 7 Daisy color 9 purple to B,b; bb for A,B or white and 7 yellow epistatic to purple flower center A,a (Duplicate color Recessive) A epistatic Complete 15 1 Shepherd's 15 triangular to B,b; B for A,B purse seed 1 ovoid epistatic to capsules A,a (Duplicate Dominant) aabb 66 cont.
Epistatic gene interaction: 1) One distinct phenotype in each phenotypic classrather than two, although two separate genes are being considered. 2) Novel or new phenotypes may appear in the F 1 and/or F 2 generations that had not appeared in the P generation. 3) Phenotypic ratio in F 2 is altered from classical ratio (ex. 9:3:4, 12:3:1, 13:3, 9:7, 15:1) 4) Masking effect. Masking (non-allelic) is not the same as dominance (allelic).
Five forms of epistasis and their corresponding F 2 phenotypic ratios: 1) Recessive (9:3:4), aa epistatic to B,b. 2) Dominant (12:3:1), A epistatic to B,b. 3) Dominant and Recessive (13:3), A epistatic to B,b, and/or bb epistatic to A,a. 4) Duplicate Recessive (9:7), aa epistatic to B,b, and/or bb epistatic to A,a. 5) Duplicate Dominant (15:1), A epistatic to B,b, and/or B epistatic to A,a.
9 A _B_ : 3 A_bb : 3 aab_ : 1 aabb 1) 9 A _B_ : 3 A_bb : 4 aab_, aabb 2) 12 A _B_, A_bb : 3 aab_ : 1 aabb 3) 13 A _B_, A_bb, aabb: 3 aab_ 4) 9 A _B_ : 7 A_bb, aab_, aabb 5) 15 A _B_, A_bb, aab_ : 1 aabb
Step - Type Epistatic Metabolic models: 1) Recessive Allele A Enzyme A Allele B Enzyme B (Precursor) Colored (Intermediate) Agouti (Final Product) 2) Duplicate Recessive Allele A Enzyme A Allele B Enzyme B Yellow (Precursor) Yellow (Intermediate) (Final Product)
Simultaneous 1) Duplicate Dominant Allele A Enzyme A Ovoid (Precursor) Triangular (Final Product) Enzyme B Allele B
Metabolic pathway models at which 3 of 1) Step-type: the 5 forms operate: Recessive (9:3:4)-2 conversions and 3 metabolites (phenotypes)-precursor, intermediate, and final product are different. Duplicate Recessive (9:7)-2 conversions and 3 metabolites (phenotypes)-precursor and intermediate are the same, but final product different. 2) Simultaneous: Duplicate Dominant (15:1)-1 conversion and 2 metabolites (phenotypes)-precursor and final product are different, with no intermediate.
..... Illustrate recessive epistasis by filling in all blanks below. Circle all gametes. aa epistatic to B,b. A_B_ = agouti mouse, A_bb = colored mouse; aab_, aabb = white mouse. P Phenotypes x Genotypes x AAbb aabb Gametes x Phenotypes x F 1 Genotypes x Gametes x F 2 Genotypes F 2 Phenotypes F 2 Phenotypic ratio..: F 2 Genotypic ratio..:... USE THE INFORMATION ABOVE TO MAKE A TESTCROSS BELOW F 1 Parent Testcross Parent Phenotypes x Genotypes x Gametes x Testcross Progeny Phenotypes Genotypes Testcross Phenotypic Ratio. Testcross Genotypic Ratio.
Illustrate recessive epistasis by filling in all blanks below. Circle all gametes. aa epistatic to B,b. A_B_ = agouti mouse, A_bb = colored mouse; aab_, aabb = white mouse. P Phenotypes colored x white. Genotypes AAbb x aabb Gametes 1/1 Ab x 1/1 ab Phenotypes agouti x agouti F 1 Genotypes AaBb x AaBb Gametes 1/4 AB 1/4 Ab 1/4 ab 1/4 ab x 1/4 AB 1/4 Ab 1/4 ab 1/4 ab F Genotypes Working space 2 F 2 Phenotypes Working space F Phenotypic ratio 9:3:4 2 F 2 Genotypic ratio 4:2:2:2:2:1:1:1:1
white USE THE INFORMATION ABOVE TO MAKE A TESTCROSS BELOW F 1 Parent Testcross Parent Phenotypes agouti x white. Genotypes AaBb x aabb Gametes 1/4 AB 1/4 x 1/1 Ab 1/4 ab 1/4 ab ab Testcross Progeny Phenotypes Genotypes. agouti 1/4 AaBb 1/4aaBb colored white 1/4 Aabb 1/4 aabb Testcross Phenotypic Ratio 2:1:1 Testcross Genotypic Ratio 1:1:1:1 63
Example of recessive epistasis (Labrador retriever coat color): A = allows for deposition of either black or brown color in coat; aa = prevents deposition of color (black or brown) pigment in coat (epistatic gene pair); B = black; b = brown. Photo (a) A B Photo (c) *aab Photo (b) A bb *This dog has a black nose and black lips and would, therefore, be aab_ (lacks black pigment in hair, but not in skin). If it was aabb it would have yellow hair and light colored skin [see nose and lips of dog in photo (b)].