Examples of Codominance. The best example, in this case, is the codominance blood type. ABO group is considered to be a codominant blood group where both father’s and mother’s blood group is expressed. It means that the properties of the blood groups exist in the ABO type.
Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked.
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Codominance
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
CODOMINANCE
2. CODOMINANCE =No blending
CODOMINANCE: - “Co” means together.
Co-dominance: It is a subtypes of Non-Mendelian heritance.
Co-dominance is believed to be a violation of the Law of Dominance.
In Heterozygous both alleles show their effects equally.
Alleles do not show blended Phenotype.
In CODOMINANCE, the “recessive”
& “dominant” traits appear together
in phenotype of hybrid organisms.
When both allele of pair are fully expressed in a heterozygote, called co-dominant alleles.
Such alleles exhibit a unique pattern of expression with heterozygous being phenotypically
distinguishable from both of the homozygous and expressing both alleles equally.
3. CODOMINANCE (Popular Examples)
CODOMINANCE:- The condition in which both alleles in a heterozygous organism are expressed.
BOTH alleles contribute to the phenotype.
The two alleles don’t blend, but are rather both present in the offspring.
Examples:-1. Checkered Chickens
2. Roan Horses
3. Roan Cows
4. Variegated flower
Some Other Example:
1. Human Blood Groups
2. Sickle Cell Anaemia
7. CODOMINANCE- in-Variegated Flower
In some instances, certain traits are co-dominant. That means that one trait cannot win out over the other from of the trait.
In offspring both traits show up equally.
In Rhododendrons, Pink is dominant with White.
This plant displays co-dominance.
Cross a pink rhododendron P with a White
rhododendron W
8. CODOMINANCE IN HUMANS
(HUMAN BLOOD)
ABO BLOOD TYPE
Que: Complete a cross with a father &
mother that both have type AB blood.
What % of their offspring could receive
each blood group?
This results in four blood types: A, B, O
and the BLENDED AB
When two alleles are BOTH expressed together
AB is co-dominant trait
9. CODOMINANCE- in- Sickle Cell Anaemia
In co-dominance, heterozygotes have their own phenotype.
This gives rise to different proportions amongst offspring of some genetic crosses
Normal haemoglobin is (RR),
Sickle Cell shaped blood cells
(SS)
People who are carries
(Heterozygous) for the disease
there is a mixture of both
normal and sickle cells.
Co-dominance caused by an abnormal Haemoglobin, the
protein that RBCs use to carry Oxygen.
10. CODOMINANCE –in- Sickle Cell Anaemia
Show the cross between an individual with sickle-cell anaemia and another who is a carrier but not sick.
Genotypes:
NS= 2
SS=2
Ratio= 1:1
Phenotypes:
Carrier= 2
Sick=2
Ratio= 1:1
11. DIFFERENCES BETWEEN INCOMPLETE DOMINANCE & CODOMINANCE
SN INCOMPLETE DOMINANCE CODOMINANCE
1. Effect of one of the two allele
is more conspicuous.
Effect of both the alleles are
equally conspicuous
2. It produces a fine mixture of
the expression of two alleles.
There is no mixing of the
expression of two alleles.
3. The effect in hybrid is
intermediate of the two
alleles.
Both the alleles produce their
effect independently.
4. The expressed phenomenon is
new. It has no allele of its own.
The expressed phenotype is
combination of two phenotypes
and their alleles.
5. The incomplete dominant
alleles has quantitative
equivalent effect. Ex.- Mirabilis
Jalapa, Antirhinum majus.
The quantitative effect is absent.
Example:-A & B Blood group alleles
of human, Roan character in cattle.
12. THINK ABOUT INCOMPLETE DOMINANCE & CODOMINANCE
Let’s say there are two alleles for the hair colour trait- RED &
BLUE
Que. What would be the resulting
phenotype of a heterozygous pair. If the
alleles showed Incomplete Dominance?
Que. What would be the resulting
phenotype of a heterozygous pair. If
the alleles showed Co- Dominance?
A) RED A) RED
B) BLUE B) BLUE
C) PURPLE C) PURPLE
D) RED and BLUE Patches D) RED and BLUE Patches
The result of incomplete dominance leads to
1.ternary phenotype
2.ternary genotype
3.intermediate phenotype
4.intermediate genotype
In case of co-dominance product is ____
a) Produced from both the alleles
b) Produced from one allele
c) Incompletely produced from both alleles
d) None are functional
13. CONCLUSION ON INCOMPLETE DOMINANCE & CODOMINANCE
In incomplete dominance- It is clear that the
dominant allele does not supress the
recessive allele and thus BLENDING occurs
and an intermediate is formed. It is a non
Mendelian traits
In co-dominance:- The case is not that like as
incomplete dominance, here BLENDING does not occur
rather an another product is formed which is neither
recessive nor dominant and contains gametes of both
dominant and recessive gametes and all the products
come in proportion.
Some MCQS are:-
1. A pink flower is an example of __________
a) Multiple alleles, b) Co-dominance, c) Incomplete dominance
2. A Checkered Chicken is an example of ____________
a) Co-dominance, b) Multiple alleles, c) Incomplete dominance
3. Blood type is an example of _____________
a) Multiple alleles, b) Co-dominance, c) Incomplete dominance
4. True/False: Fathers can pass sex linked traits like colour blindness on to their sons.
5. True /False: A blood has the genotypes AA and AO.
14. 1. Both alleles are fully expressed
Complete dominance
Partial dominance
Codominance
2. Exhibits Mendelian pattern
Complete dominance
Partial dominance
Codominance
3. Which is not an example of codominance?
Black and white coat
White-spotted red flower
Pink flower
4. A variant of a gene
Allele
Chromosome
Nucleotide
5. It means the alleles occupying the same locus are different
Genotype
Homozygous
Heterozygous
6. The gene by which the ABO blood group system
is controlled is classified as
1.gene 'I'
2.gene A'
3.gene 'B'
4.gene 'O'
7. The kind of situation in which alleles of gene pair
are expressed completely by themselves is called
1.segregation
2.dependent assortment
3.co-dominance
4.dominance
8. The examples of deviations from laws of
inheritance proposed by Mendel includes
1.evolutionary dominance only
2.incomplete dominance only
3.co-dominance
4.evolutionary and incomplete dominance
9. The situation in which no allele is
dominant over the other is called
1.assorted dominance
2.segregated dominance
3.complete dominance
4.incomplete dominance