Prepared for B. Sc. III Botany students, based on the syllabus prescribed by Dr. Babasaheb Ambedkar Marathwada University, Aurangabad.

1. B.SC. III YEAR: SEMESTER-VI
GENETICS AND BIOTECHNOLOGY
INCOMPLETE DOMINANCE
Dr. Anjali Naik
Head, Dept. of Botany
SBES COLLEGE OF SCIENCE

5. EXPLANATION OF INCOMPLETE
DOMINANCE
• Deviation of Monohybrid inheritance.
• Definition: When none of the two alleles, controlling the character, are completely
dominant or recessive, both of them express phenotypically in F1 heterozygous
condition and when their expression show uniform blending, it is called as Incomplete
inheritance.
• F2 has same genotypic and phenotypic ratio: 1:2:1
• Phenotypic ratio modified with 3 classes, instead 2, as seen in classic Mendelian Monohybrid
inheritance and ratio gets modified as 1:2:1
• Example: Flower colour in Snapdragon, Mirabilis jalapa

6. HOW INCOMPLETE DOMINANCE CAN
BE EXPLAINED?
• Parents: phenotypes: Red flowered and white flowered.
• Genotypes of parents: Red flowered – RR. 2. White flowered:WW
• Gametes of Red cow: all gametes will have allele- R
• Gametes of white bull:All gametes will have allele- W
• Red flowered X White Flowered
• RR X WW
• F1 :All individuals will have RW genotype and Pink flowered
• Selfing of F1 : RW X RW

7. 7
Male Parent Female parent
R W
R RR (Red) RW(Pink)
W RW (Pink) WW(White)
Punnett square Incomplete dominance for
proportions of F2
F2 Genotypic ratio: RR 1: RW 2:WW 1
Phenotypic ratio: Red 25%: PINK 50%:White 25%

8. OTHER EXAMPLES OF INCOMPLETE
DOMINANCE
COAT COLOUR OF HORSES
FEATHERS IN ANDULASIAN FOWLS

9. ASSIGNMENT ON INCOMPLETE DOMINANCE
1. In radishes, red and white are pure-breeding colors, while hybrids are purple. If a
red radish is crossed with a white radish, what will be the phenotype of the F2
generation (assuming the F1 generation self-pollinates)? Show the Punnett Square.
2. In Andulasian fowls, black individuals (B) and white individuals (W) are homozygous.
A homozygous black bird is crossed with a homozygous white bird.The offspring are
all bluish-gray. Show the cross as well as the genotypes and phenotypes of the
parents and offspring.