Codominance Questions in English

(B) In codominance,both the alleles of an allelomorphic pair express themselves equally in $F_1$ hybrids. This results in a $1:2:1$ ratio both genotypically and phenotypically in the $F_2$ generation,where each allele maintains its independent effect.

(C) In codominance,both alleles of a gene pair express themselves equally in the $F_1$ hybrid.
In the case of shorthorn cattle,the cross between red $(R_1R_1)$ and white $(R_2R_2)$ parents results in offspring with both red and white patches,known as roan $(R_1R_2)$.
Since both alleles are expressed simultaneously without blending,this phenomenon is known as codominance.

(A) The $MN$ blood group system is determined by a single gene locus with two alleles,$L^M$ and $L^N$.
These two alleles exhibit co-dominance,meaning that in the heterozygote $(L^M L^N)$,both alleles are expressed equally.
As a result,individuals with the genotype $L^M L^M$ have $M$ antigens,those with $L^N L^N$ have $N$ antigens,and those with $L^M L^N$ have both $M$ and $N$ antigens on their red blood cells.
Therefore,the $MN$ factors are due to two co-dominant genes $M$ and $N$.

(B) Codominance is a condition in a heterozygote where both members of an allelic pair contribute to the phenotype.
This results in a mixture of the phenotypic traits produced in either homozygous condition.
For example,in cattle,the cross of red $\times$ white produces roan offspring,whose coat consists of both red and white hair.

(A) In $Codominance$,the alleles of a gene pair are both expressed in the heterozygote. This means that both the dominant and recessive alleles express their traits simultaneously in the offspring,resulting in a phenotype that shows characteristics of both parents. $A$ classic example is the $ABO$ blood grouping system in humans,where both $I^A$ and $I^B$ alleles are expressed equally.

(D) Codominance is a phenomenon where,in a heterozygous condition,both alleles of a gene pair express themselves independently.
As a result,the phenotype of the offspring is a combination of both parental traits rather than a blend or the dominance of one over the other.
$A$ classic example is the $ABO$ blood grouping system in humans,where individuals with the $I^A I^B$ genotype express both $A$ and $B$ antigens on their red blood cells.

(C) In the $ABO$ blood group system,the gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
When both $I^A$ and $I^B$ are present together in an individual,they both express their own types of sugars because of codominance.
This results in the $AB$ blood type.
Therefore,both alleles are expressed simultaneously.

(A) In human $ABO$ blood grouping,the gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
When $I^A$ and $I^B$ are present together,both alleles express themselves equally in the individual,resulting in the $AB$ blood group.
This phenomenon,where both alleles of a gene pair express themselves equally in the heterozygote,is known as codominance.

(C) Codominance is a phenomenon in which both alleles of a gene pair express themselves equally in the $F_1$ generation.
In this condition,the $F_1$ hybrid does not show an intermediate phenotype (as in incomplete dominance) or resemble only one parent (as in complete dominance).
Instead,the $F_1$ generation shows the traits of both parents simultaneously.
Therefore,the $F_1$ phenotype resembles both parents.

(A) In codominance,both alleles of a gene pair express themselves equally in the $F_1$ generation.
This means that the heterozygote shows the characteristics of both parents simultaneously.
For a monohybrid cross involving codominance (e.g.,$AB$ blood group or coat color in cattle),the genotypic ratio is $1:2:1$ (homozygous dominant : heterozygous : homozygous recessive).
Since the heterozygote expresses both traits distinctly,the phenotypic ratio also becomes $1:2:1$.

(A) In cattle,coat color exhibits codominance. Let $R$ represent the red allele and $W$ represent the white allele. The genotype for red is $RR$,white is $WW$,and roan is $RW$.
$1$. Cross between roan bull $(RW)$ and cow $A$ $(RW)$: The offspring genotypes are $1 RR : 2 RW : 1 WW$. Thus,the proportion of roan $(RW)$ offspring is $2/4$ or $1/2$.
$2$. Cross between roan bull $(RW)$ and cow $B$ $(RR)$: The offspring genotypes are $1 RR : 1 RW$. Thus,the proportion of roan $(RW)$ offspring is $1/2$.
$3$. Cross between roan bull $(RW)$ and cow $C$ $(WW)$: The offspring genotypes are $1 RW : 1 WW$. Thus,the proportion of roan $(RW)$ offspring is $1/2$.
Comparing the ratios of roan offspring: $1/2 : 1/2 : 1/2$,which simplifies to $1:1:1$ in terms of probability,but based on the provided options,the question implies the ratio of roan offspring in the respective crosses. Given the standard Mendelian cross outcomes for these genotypes,the correct proportion of roan offspring is $1/2$ for each cross.

(B) In $Codominance$,both alleles of a gene pair are expressed equally in the $F_1$ generation.
Neither allele is dominant or recessive over the other.
An example of this is the $ABO$ blood grouping system in humans,where both $I^A$ and $I^B$ alleles are expressed simultaneously in individuals with the $AB$ blood type.

(C) In cattle,coat color is an example of codominance.
Roan color is represented by the genotype $RW$ (where $R$ is red and $W$ is white).
$A$ roan cow has the genotype $RW$.
$A$ white bull has the genotype $WW$.
When we cross $RW$ (roan) $\times$ $WW$ (white):
- The gametes produced by the roan cow are $R$ and $W$.
- The gametes produced by the white bull are $W$ and $W$.
- The resulting offspring genotypes are $RW$ (roan) and $WW$ (white) in a $1:1$ ratio.
Therefore,the phenotypic ratio of the offspring is $1$ roan : $1$ white,which is $1:1$.

(B) : The phenomenon of expression of both the alleles in a heterozygote is called codominance.
Both alleles do not show a dominance-recessive relationship and are able to express themselves independently when present together.
As a result,the heterozygous condition has a phenotype that is a combination of both homozygous genotypes.
For example,the alleles for blood group $A$ $(I^A)$ and blood group $B$ $(I^B)$ are codominant,so when they occur together in an individual,they produce blood group $AB$.

(C) The correct answer is $(c)$.
The phenomenon where both alleles of a gene pair express themselves equally in a heterozygote is known as codominance.
In the case of $ABO$ blood grouping in humans,the alleles $I^A$ and $I^B$ are codominant.
When both $I^A$ and $I^B$ are present together in an individual (genotype $I^A I^B$),both alleles express their respective antigens ($A$ and $B$ proteins) on the surface of red blood cells independently.
This results in the $AB$ blood group phenotype,which is distinct from both the $A$ blood group and the $B$ blood group,demonstrating that neither allele is dominant or recessive over the other.

(B) : In codominance,both alleles are able to express themselves independently when present together,resulting in a phenotype that shows the characteristics of both parental homozygous phenotypes.
For example,the roan coat colour in cattle is a result of the codominance of alleles for white and red coat colours,where the offspring exhibits both white and red patches simultaneously.

(C) In the $ABO$ blood grouping system,the gene $I$ has three alleles: $I^A$,$I^B$,and $i$.
Alleles $I^A$ and $I^B$ are dominant over $i$,but when both $I^A$ and $I^B$ are present together,they both express themselves equally.
This phenomenon,where both alleles of a gene pair express themselves simultaneously in a heterozygote,is known as co-dominance.
Therefore,the genotype $I^AI^B$ results in blood group $AB$,which is a classic example of co-dominance.

(A) In $Codominance$,the alleles of a gene pair are both expressed in the heterozygous condition. This means that neither allele is dominant over the other,and both produce their independent effects simultaneously in the phenotype. $A$ classic example is the $ABO$ blood grouping system in humans,where individuals with the $I^A I^B$ genotype express both $A$ and $B$ antigens on their red blood cells.

(A) In $Codominance$,both alleles of a gene pair are expressed equally in the $F_1$ generation. As a result,the $F_1$ progeny resembles both parents simultaneously. $A$ classic example is the $AB$ blood group system in humans,where both $I^A$ and $I^B$ alleles are expressed,resulting in the $AB$ blood type.

(A) The $ABO$ blood grouping in humans is controlled by the gene $I$. The gene $I$ has three alleles $I^A$,$I^B$,and $i$.
When $I^A$ and $I^B$ are present together,they both express their own types of sugars (antigens) because of codominance.
In the given cross,both parents have $AB$ blood group (genotype $I^A I^B$).
The cross $I^A I^B \times I^A I^B$ results in offspring with genotypes $I^A I^A$ ($A$ blood group),$I^A I^B$ ($AB$ blood group),and $I^B I^B$ ($B$ blood group) in the ratio $1:2:1$.
Since both alleles $I^A$ and $I^B$ are expressed equally in the $AB$ phenotype,this is an example of codominance.

(D) Codominance is a phenomenon where both alleles of a gene pair are expressed equally in the heterozygote.
Unlike incomplete dominance,where the phenotype is a blend,in codominance,both parental traits appear distinctly.
$A$ classic example is the $ABO$ blood grouping system in humans,where individuals with genotype $I^A I^B$ express both $A$ and $B$ antigens on their red blood cells.

(N/A) Codominance is a phenomenon where both alleles of a gene pair are expressed equally in the heterozygote,meaning neither allele is dominant or recessive over the other.
In this case,the phenotype of the $F_1$ generation resembles both parents.
An excellent example of codominance in humans is the $ABO$ blood grouping system.
The $ABO$ blood groups are controlled by the gene $I$. The plasma membrane of red blood cells has sugar polymers that protrude from its surface,and the kind of sugar is controlled by the gene $I$.
The gene $I$ has three alleles: $I^A$,$I^B$,and $i$. The alleles $I^A$ and $I^B$ produce slightly different forms of the sugar,while the allele $i$ does not produce any sugar.
Since humans are diploid $(2n)$ organisms,each person possesses any two of the three alleles. The alleles $I^A$ and $I^B$ are completely dominant over $i$,so when $I^A$ and $i$ are present,only $I^A$ is expressed. Similarly,when $I^B$ and $i$ are present,only $I^B$ is expressed.
However,when $I^A$ and $I^B$ are present together,they both express their own types of sugars. This is codominance.
There are $6$ different genotypes possible for the $ABO$ blood group system.

Allele from Parent $1$	Allele from Parent $2$	Genotype of Offspring	Blood Type of Offspring
$I^A$	$I^A$	$I^A I^A$	$A$
$I^A$	$I^B$	$I^A I^B$	$AB$
$I^A$	$i$	$I^A i$	$A$
$I^B$	$I^A$	$I^A I^B$	$AB$
$I^B$	$I^B$	$I^B I^B$	$B$
$I^B$	$i$	$I^B i$	$B$
$i$	$i$	$i i$	$O$

(N/A) Co-dominance is a phenomenon in which both alleles of a gene pair express themselves equally in the $F_1$ generation. In this case,the $F_1$ generation resembles both parents. $A$ classic example of co-dominance is the $ABO$ blood grouping system in humans,where individuals with $I^A I^B$ genotype express both $A$ and $B$ antigens on the surface of their red blood cells.

(D) Mendel's laws,specifically the Law of Dominance and the Law of Segregation,describe the inheritance of traits where one allele is dominant over the other.
Option $D$ describes a phenomenon known as codominance,where both alleles for a gene are expressed simultaneously in the heterozygote (e.g.,$AB$ blood group in humans).
Since Mendel's experiments were based on complete dominance,codominance is an exception to his laws.

(C) In cattle,the coat color inheritance often shows $Co-dominance$.
When a white-coated bull is crossed with a red-coated cow,the offspring ($F_1$ generation) exhibit a roan coat color.
In roan cattle,both red and white hair patches are present simultaneously,meaning both alleles are expressed equally in the phenotype.
This phenomenon,where both alleles of a gene pair express themselves equally in the heterozygote,is known as $Co-dominance$.

(A) Codominance is a phenomenon where both alleles of a gene pair express themselves equally in the heterozygote.
In the case of human $ABO$ blood grouping,the gene $I$ has three alleles: $I^{A}$,$I^{B}$,and $i$.
When $I^{A}$ and $I^{B}$ are present together in an individual,both alleles express their respective sugars on the surface of red blood cells.
Therefore,the genotype $I^{A}I^{B}$ represents codominance,resulting in blood type $AB$.

(B) The phenomenon described is $Codominance$. In $Codominance$, both alleles of a gene pair express themselves equally in the $F_1$ generation, meaning neither allele is dominant or recessive over the other. A classic example of $Codominance$ in humans is the $ABO$ blood group system, specifically the $AB$ blood type, where both $I^A$ and $I^B$ alleles are expressed simultaneously. $Mirabilis$ $jalapa$ (Four o'clock plant) exhibits $Incomplete$ $Dominance$, not $Codominance$. $Pleiotropism$ refers to a single gene influencing multiple phenotypic traits. Therefore, the correct answer is $Blood$ $group$.

(B) The phenomenon where both alleles of a gene pair express themselves simultaneously in a heterozygous condition is known as $Codominance$.
In the case of human $ABO$ blood grouping, the $I^A$ and $I^B$ alleles are codominant.
When both $I^A$ and $I^B$ are present together in an individual, they both express their respective sugar polymers on the surface of red blood cells, resulting in the $AB$ blood type.
Therefore, $Codominance$ is observed in blood groups.

(A) Among the given options, only codominance does not follow Mendel's laws.
The phenomenon where both alleles of a gene pair express themselves simultaneously in a heterozygote is called codominance. As a result, the phenotype is distinct from both homozygous parents.
Key points:
$1.$ Codominance is an exception to the Law of Dominance.
$2.$ $ABO$ blood grouping in humans is a classic example of codominance and multiple alleles.
$3.$ The gene $I$ has three alleles: $I^{A}, I^{B},$ and $i$. $I^{A}$ and $I^{B}$ produce different forms of sugar, while $i$ produces no sugar.
$4.$ When $I^{A}$ and $I^{B}$ are present together, both express themselves, resulting in blood type $AB$.

Genotype of Offspring	Blood Type of Offspring
$I^{A} I^{A}$	$A$
$I^{A} I^{B}$	$AB$
$I^{A} i$	$A$
$I^{B} I^{B}$	$B$
$I^{B} i$	$B$
$ii$	$O$

Independent assortment and the law of purity of gametes (segregation) are fundamental Mendelian principles.

(B) In codominance,both alleles of a gene pair express themselves equally in the phenotype of a heterozygote.
In the case of $AB$ blood group,the alleles $I^A$ and $I^B$ are codominant.
When both $I^A$ and $I^B$ are present together,both produce their respective antigens ($A$ and $B$) on the surface of $RBCs$ simultaneously.
Therefore,the $AB$ blood group is the classic example of codominance.

(C) Codominance is a phenomenon where both alleles of a gene pair express themselves equally in the heterozygote. In humans,the $ABO$ blood group system is controlled by the $I$ gene. The $I$ gene has three alleles: $I^A$,$I^B$,and $i$. When both $I^A$ and $I^B$ are present together in an individual,they both express their respective sugars,resulting in $AB$ blood type. This is a classic example of codominance.

(B) In codominance,both alleles of a gene pair express themselves equally in the $F_1$ hybrid.
In short-horned cattle,the allele for red coat colour $(R)$ and the allele for white coat colour $(r)$ are both expressed in the heterozygote $(Rr)$,resulting in a roan phenotype (a mixture of red and white hairs).
Therefore,this is a classic example of codominance.

(N/A) Co-dominance is the phenomenon in which two alleles express themselves independently when present together in an organism.
In other words, it is the phenomenon in which the offspring shows resemblance to both parents, e.g., $ABO$ blood grouping in humans.
$ABO$ blood groups are controlled by the gene $I$.
The plasma membrane of the red blood cells has sugar polymers that protrude from its surface, and the kind of sugar is controlled by the gene.
The gene $I$ has three alleles: $I^{A}$, $I^{B}$, and $i$.
The alleles $I^{A}$ and $I^{B}$ produce a slightly different form of a sugar, while allele $i$ does not produce any sugar.
In humans, each person possesses any two of the three $I$ gene alleles.
$I^{A}$ and $I^{B}$ are completely dominant over $i$.
When $I^{B}$ and $i$ are present, only $I^{B}$ expresses (because $i$ does not have any sugar); the same is the case with $I^{A}$ and $i$.
But when $I^{A}$ and $I^{B}$ are present together, they both express their own types of sugars; this is due to co-dominance.
Therefore, the red blood cells have both $A$ and $B$ types of sugars.
Since there are three different types of alleles, there can be six different combinations.
Hence, a total of six different genotypes of the human $ABO$ blood types are present, as given below in the table:
Table: Genetic Basis of Blood Groups in Human Population

$Allele \text{ from Parent } 1$	$Allele \text{ from Parent } 2$	$Genotype \text{ of offspring}$	$Blood \text{ types of offspring}$
$I^{A}$	$I^{A}$	$I^{A} I^{A}$	$A$
$I^{A}$	$I^{B}$	$I^{A} I^{B}$	$AB$
$I^{A}$	$i$	$I^{A} i$	$A$
$I^{B}$	$I^{A}$	$I^{A} I^{B}$	$AB$
$I^{B}$	$I^{B}$	$I^{B} I^{B}$	$B$
$I^{B}$	$i$	$I^{B} i$	$B$
$i$	$i$	$i i$	$O$

(B) In a heterozygous condition,when both alleles of a gene pair express themselves independently and fully,the phenomenon is known as $Co-dominance$.
An example of this is the $ABO$ blood grouping system in humans,where both $I^A$ and $I^B$ alleles are expressed equally in individuals with the $AB$ blood type.

(A) In blood group $AB$,the alleles for both antigens,$A$ $(I^A)$ and $B$ $(I^B)$,are expressed equally and independently,resulting in the genotype $I^A I^B$ (phenotype $AB$).
Since both alleles express themselves simultaneously in the heterozygote,this phenomenon is known as co-dominance.

(D) Intragenic interactions occur between the alleles of the same gene.
Examples of intragenic interactions include co-dominance,incomplete dominance,and multiple alleles.
Epistasis,polygene,and pleiotropy are examples of intergenic (or non-allelic) interactions.