▶️ Answer/Explanation
- Answer: CcRr
- Explanation:
The parental genotypes CCrr (white) and ccRR (white) produce gametes Cr and cR respectively. Their fusion yields F1 hybrids with genotype CcRr, showing complementation where both dominant alleles (C and R) are required for purple pigment production.
- Key Points:
- Gene Interaction: Two unlinked genes (C and R) interact epistatically, where both dominant alleles are required for purple color (C_R_).
- F2 Genotypes: Selfing CcRr × CcRr produces:
- 9/16 C_R_ (purple)
- 3/16 C_rr (white)
- 3/16 ccR_ (white)
- 1/16 ccrr (white)
- Ratio Formation: The 9:3:3:1 Mendelian ratio becomes 9:7 because three genotypic classes (3+3+1) all produce the same white phenotype.
- Punnett Square Visualization:
Gametes: CR, Cr, cR, cr → 9 purple : 7 white
- Answer: 1 purple : 3 white
- Explanation:
Possible gametes:
- Ccrr produces Cr and cr
- ccRr produces cR and cr
Offspring genotypes and phenotypes:
1 CcRr (purple), 1 Ccrr (white), 1 ccRr (white), 1 ccrr (white)
Genotype Phenotype Ratio CcRr Purple 1 Others White 3
CcRr ✔
a. Two unlinked genes (C and R) interact epistatically, requiring both dominant alleles for purple color (C_R_) ✔
b. Selfing CcRr × CcRr produces 9/16 C_R_ (purple), 3/16 C_rr (white), 3/16 ccR_ (white), 1/16 ccrr (white) ✔
c. The 9:3:3:1 ratio becomes 9:7 as three genotypic classes (C_rr, ccR_, ccrr) produce white phenotype ✔
1 purple : 3 white ✔