“Incomplete dominance is a form of intermediate inheritance in which one allele for a particular trait is not expressed completely over its paired allele.” What is Incomplete Dominance? Incomplete dominance is a form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype. It shows that alleles of red and white coloured flowers were unable to dominate the other, thus resulting in incomplete dominance. Thus, the law of incomplete dominance says that when none of the two alleles exerts complete dominance over the other, the offspring will be a mixture of parents’ phenotypes. Aside from flowering plants, incomplete dominance takes place in human beings and animals as well. One such incomplete dominance example in human beings is that the growth of wavy hair. The phenomenon in which two true-breeding parents crossed to produce an intermediate offspring (also known as heterozygous) is called incomplete dominance. ... In incomplete dominance, the variants (alleles) are not expressed as dominant or recessive; rather, the dominant allele is expressed in a reduced ratio.

1. Rajendra Chavhan
NON-MENDELIAN INHERITANCE
PRESENTED BY
Dr. RAJENDRA CHAVHAN
Assistant Professor in Zoology,
Mahatma Gandhi Arts, Science and
Late N. P. Commerce College Armori, District Gadchiroli
INCOMPLETE DOMINANT TRAITS

2. “The process of genetic transmission of traits from Parents to offspring is called inheritance”.
It is also defined as the sum of the characteristics genetically transmitted from PARENTS TO OFFSPRING.
Mendelian’s inheritance is that which follows Mendel’s Laws
MENDELIAN INHERITANCE:
MENDEL’S LAW IS NOT PERFECT
Was he just plain wrong ?
Truth is that his laws are correct and he did explain how genetics
work.
Real life is just more complicated than peas plant.
Shortly people began to notice that not all traits are
“Mendelians”.
This means, they do NOT follow Mendel’s Laws.

3. Altering Mendel’s Ratios
Two different types of complications:
1. Genotypic ratios follow Mendel’s Laws, but phenotypes do not. Somehow
the underlying genotypic ratios are hidden.
2. Mendel’s laws do not apply. Both genotypes and phenotypes are not
following Mendel’s laws.
Mendel’s laws of inheritance:
1. Law of Dominance
2. Law of segregation or law of purity of gametes
3. Law of independent Assortment.

4. WHAT DOES NON-MENDELIAN INHERITANCE MEAN?
“NOT ALL TRAITS ARE AS SIMPLE AS DOMINANT AND RECESSIVE”
TYPES OF NON-MENDELIAN INHERITANCE
1. ALLELIC OR INTRA ALLELIC GENE INTERACTION
2. NON-ALLELIC OR INTER ALLELIC GENE INTERACTION
Some traits:-
Have more than just two alleles or variations.
Have two dominant alleles.
Are only passed on via sex chromosomes.
Are the result of 100’s of genes being expressed.

5. Introduction:
 Alleles of the same gene interact in such a way to produce new
Characters.
 It is a type of Gene Interaction.
 It is a Non-Mendelian Inheritance.
 It was discovered by Gregor Johan Mendel in his Monohybrid study with
garden pea plants (Pisum sativum).
 Thus in the beginning of his report (Experiments on Plant Hybridization,
Mendel 1865), he introduced the terms dominant and recessive.
 These dominance relations involve intra allelic rather than “inter allelic”
gene interaction. The Latin prefix "intra" means within or inside;
"inter" means between or among (BORROR 1988).
ALLELIC OR INTRA ALLELIC GENE INTERACTION
Subtypes:
a) Complete Dominance
b) Incomplete Dominance
c) Co dominance or Blending
inheritance
d) Cumulative Genes or Multiple
Genes
e) Pleiotropism

8. INCOMPLETE DOMINANT TRAITS:
INCOMPLETE = not fully
Incomplete Dominance= When two dominant traits are partially expressed together at the
same time, resulting in a blending appearance.
Example:
Some flowers can be HOMOZYGOUS DOMINANT AND RED crosses with the some flowers
can be HOMOZYGOUS DOMINANT AND WHITE, their offspring flowers can be heterozygous,
they look PINK (Like a blending of RED + White).
Neither allele is Dominant and heterozygous individuals have an intermediate phenotype.

10. Some alleles are neither Dominant nor Recessive.
One allele is not completely Dominant over another.
INCOMPLETE DOMINANCE
Example:
1. Snapdragon flower: Mirabilis jalapa
2. Antirhinum majus
•Chickens with blue feathers are an example of incomplete
dominance. When a black and a white chicken reproduce and neither
allele is completely dominant, the result is a blue-feathered bird.
•Incomplete dominance was first
recorded in plants.
•The German scientist Joseph
Kolreuter (1760) bred RED and
WHITE carnations, expecting to
get offspring with the dominant
red coloration. Instead, many
came up PINK!
•Kolreuter found that neither allele
was fully dominant in his flowers
and identified the concept of
incomplete dominance.

11. •On the subject of dogs, lots of labradoodles have wavy hair. Just like humans,
that comes from having straight-haired and curly-haired parents. The result is
an intermediate inheritance: the wavy-haired labradoodle.
•The cream gene in horses is a classic incomplete dominant. When paired with a
red allele, the cream allele produces horses with golden coats such as palominos
and buckskins.
Incomplete dominance in animals is most widely studied in domestic animals since it's important for their
health, appearance, and value. Here are several examples of the effects of incomplete dominance in animals:
INCOMPLETE DOMINANCE (Blended inheritance)
•Chickens with blue feathers are an example of incomplete dominance. When a black and a white chicken
reproduce and neither allele is completely dominant, the result is a blue-feathered bird.
•When a long-furred Angora rabbit and a short-furred Rex rabbit reproduce, the result can be a rabbit with
fur longer than a Rex, but shorter than an Angora. That's a classic example of incomplete dominance
producing a trait different from either of the parents.
•Tail length in dogs is often determined by incomplete dominance. Pups of long-tailed and short-tailed
parents often split the difference and have medium-length tails.

12. Four-o-clocks are flowering plants
Pink snapdragons
The fruit color of eggplants
The disease familial hypercholesterolemia (FH)
Tay-Sachs Disease
Eye color
An example of incomplete dominance in humans
An example of incomplete dominance in Plants
Incomplete dominance
in snapdragon flowers
superficially appears like
blending inheritance.

14. A CROSSBETWEEN TWO INDIVIDUALS DIFFERING IN ONECHARACTER PAIR
MONOHYBRID
CROSS