In peanuts, a plant may either bunch or run as it grows. Two different strains o
ID: 67735 • Letter: I
Question
In peanuts, a plant may either bunch or run as it grows. Two different strains of peanut, V4 and G2 are both true breeding, and both bunch. V4 (bunching) × V4 (bunching) all bunching G2 (bunching) × G2 (bunching) all bunching The cross of these two strains, however, results in plants that run. G2 (bunching) × V4 (bunching) F1: all running The self cross of the F1 generation results in a 9:7 ratio of offspring plants. F1 (running) × F1 (running) F2: 9 running : 7 bunching What is the genetic basis of the inheritance pattern for runner and bunch growth?
Explanation / Answer
This is simple case of epistasis where two genes control the same trait.
Lets say, dominant allele “C” and allele “P” control bunching. However, when both alleles are present they complement each other to produce a phenotype of runner. Recessive alleles produce no product.
Genotype of V4: CCpp Gametes produced: all Cp
Genotype of G2: ccPP Gametes produced: all cP
F1 genotype: CcPp (all runners)
Gametes produced by F1 offspring: CP, Cp, cP, cp
Make punnet square
CP
Cp
cP
cp
CP
CCPP
CCPp
CcPP
CcPp
Cp
CCPp
CCpp
CcPp
Ccpp
cP
cCPP
cCPp
ccPP
ccPp
cp
cCPp
cCpp
ccPp
ccpp
Runners: CCPP, CCPp, CcPP, CcPp, CCPp, CcPp, CcPP, CcPp, CcPp
Bunching: CCpp, Ccpp, ccPP, ccPp, cCpp, ccPp, ccpp
Phenotypic ratio: 9 : 7
CP
Cp
cP
cp
CP
CCPP
CCPp
CcPP
CcPp
Cp
CCPp
CCpp
CcPp
Ccpp
cP
cCPP
cCPp
ccPP
ccPp
cp
cCPp
cCpp
ccPp
ccpp