Incomplete dominance Questions in English

(B) The phenomenon of incomplete dominance was observed by Carl Correns in $1903$.
While working with the plant $Mirabilis$ $jalapa$ (four-o'clock plant),he observed that when a red-flowered variety is crossed with a white-flowered variety,the resulting $F_1$ hybrid is pink.
Furthermore,the $F_2$ generation exhibits a phenotypic ratio of $1$ red : $2$ pink : $1$ white.
This result demonstrates that neither allele is completely dominant over the other,hence the term incomplete dominance.

(A) 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 is also known as "blending inheritance" because the traits appear to blend in the offspring.
It is also referred to as "intermediate inheritance" or "partial dominance".

(D) In a typical Mendelian monohybrid cross,the phenotypic ratio is $3:1$.
However,in cases of incomplete dominance,the dominant allele does not completely mask the recessive allele.
As a result,the heterozygote $(Aa)$ exhibits an intermediate phenotype between the dominant and recessive traits.
Therefore,the $F_2$ generation shows a phenotypic ratio of $1$ (homozygous dominant) : $2$ (heterozygous intermediate) : $1$ (homozygous recessive),which matches the genotypic ratio.

(B) This is an example of Incomplete Dominance.
In $Mirabilis \text{ } jalapa$ (Four O'clock plant), the allele for red flower colour $(R)$ is incompletely dominant over the allele for white flower colour $(r)$.
When homozygous red $(RR)$ and white $(rr)$ plants are crossed, the $F_1$ generation $(Rr)$ produces pink flowers.
When $F_1$ individuals $(Rr)$ are self-crossed $(Rr \times Rr)$, the resulting $F_2$ generation shows the following genotypes: $1 RR$ (red) : $2 Rr$ (pink) : $1 rr$ (white).
Thus, the phenotypic ratio is $1 : 2 : 1$.

(D) In Snapdragon ($Antirrhinum$ $sp.$),the inheritance of flower colour exhibits incomplete dominance.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$,the $F_1$ progeny $(Rr)$ does not show the dominant trait (red) but instead exhibits an intermediate phenotype,which is pink.
This occurs because the dominant allele is not completely dominant over the recessive allele,resulting in a blending effect in the heterozygote.

(B) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele, resulting in an intermediate phenotype in the $F_1$ generation.
This phenomenon is observed in $Antirrhinum$ $majus$ (snapdragon) and $Mirabilis$ $jalapa$ ($4$ $O'clock$ plant).
In $Pisum$ $sativum$ (garden pea), complete dominance is observed, not incomplete dominance.
Therefore, the correct option is $B$.

(B) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele, resulting in an intermediate phenotype in the heterozygote.
$Mirabilis \text{ } jalapa$ (Four o'clock plant) is a classic example of incomplete dominance, where crossing red-flowered plants with white-flowered plants produces pink-flowered offspring in the $F_1$ generation.
$Pisum \text{ } sativum$ exhibits complete dominance.
Therefore, the correct option is $(b)$.

(B) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele, resulting in a phenotype that is an intermediate of the two parents.
In $Mirabilis \text{ } jalapa$ (also known as the $4 \text{ } o'clock$ plant), when a red-flowered plant is crossed with a white-flowered plant, the $F_1$ generation produces pink-flowered plants.
This intermediate phenotype is a classic example of incomplete dominance.

(D) The correct answer is $(d)$ Incomplete dominance.
Incomplete dominance is a phenomenon in which the $F_1$ hybrid phenotype is intermediate between the two parental phenotypes.
This occurs because neither of the two alleles is completely dominant over the other.
For example, in $Mirabilis$ $jalapa$ (four o'clock plant), a cross between red-flowered plants $(RR)$ and white-flowered plants $(rr)$ results in $F_1$ hybrids with pink flowers $(Rr)$, which is an intermediate trait.

(C) In incomplete dominance,the dominant allele does not completely mask the effect of the recessive allele,resulting in an intermediate phenotype in the $F_1$ generation.
In the $F_2$ generation,the phenotypic ratio is $1:2:1$ (e.g.,$1$ red : $2$ pink : $1$ white in Mirabilis jalapa).
The genotypic ratio is also $1:2:1$ (e.g.,$1$ $RR$ : $2$ $Rr$ : $1$ $rr$).
Therefore,in incomplete dominance,the genotypic ratio is equal to the phenotypic ratio $(1:2:1)$.

(C) This is an example of incomplete dominance,a phenomenon where neither of the two alleles is completely dominant over the other.
In this case,the $F_1$ generation offspring $(Rw)$ exhibit a phenotype that is an intermediate blend of the parental traits (pink),rather than expressing the dominant trait fully.
This serves as an exception to Mendel's law of dominance.

(A) In incomplete dominance,the dominant allele does not completely mask the recessive allele.
As a result,the heterozygote exhibits an intermediate phenotype.
In the $F_2$ generation of a monohybrid cross,the genotypic ratio is $1:2:1$ (homozygous dominant : heterozygous : homozygous recessive).
Because the heterozygote shows a distinct intermediate phenotype,the phenotypic ratio also becomes $1:2:1$.

(A) In incomplete dominance, the dominant allele does not completely mask the effect of the recessive allele.
As a result, the heterozygous condition shows an intermediate phenotype.
For example, in the snapdragon $(Antirrhinum majus)$, the cross between red $(RR)$ and white $(rr)$ flowers results in pink $(Rr)$ flowers in the $F_1$ generation.
When $F_1$ plants $(Rr)$ are self-pollinated, the $F_2$ generation shows a phenotypic ratio of $1:2:1$ (Red:Pink:White) and a genotypic ratio of $1:2:1$ $(RR:Rr:rr)$.
Therefore, the genotypic ratio is equal to the phenotypic ratio.

(A) The phenomenon of incomplete dominance is observed in $Mirabilis$ $\text{jalapa}$ (Four o'clock plant) and $Antirrhinum$ $\text{majus}$ (Snapdragon). In these plants, the $F_1$ generation does not resemble either of the two parents but exhibits an intermediate phenotype. This contradicts Mendel's law of dominance, which states that one allele completely masks the expression of the other. Therefore, $Mirabilis$ is the correct answer.

(B) 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 phenotype. This phenomenon was first discovered and reported by Carl Correns in $1903$ while working on the $4$ o'clock plant $(Mirabilis jalapa)$. In his experiments, crossing red-flowered and white-flowered plants resulted in pink-flowered offspring in the $F_1$ generation.

(A) The Andalusian fowl exhibits incomplete dominance. When a black-feathered fowl $(BB)$ is crossed with a white-feathered fowl $(WW)$,the $F_1$ generation offspring are blue-feathered $(BW)$. This is a classic example where the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygous parents. However,in the context of the provided options,'Blending inheritance' is an outdated term sometimes used to describe this phenomenon,but 'Incomplete dominance' is the correct scientific term. Since 'Incomplete dominance' is not listed,and the question asks for the pattern,it is often associated with the concept of incomplete dominance or intermediate inheritance.

(A) In $Mirabilis \text{ } jalapa$, the inheritance of flower color shows incomplete dominance.
$1$. The cross between red $(RR)$ and white $(rr)$ produces pink $(Rr)$ flowers in the $F_1$ generation.
$2$. Selfing the $F_1$ generation $(Rr \times Rr)$ results in an $F_2$ phenotypic ratio of $1$ Red $(RR)$ : $2$ Pink $(Rr)$ : $1$ White $(rr)$.
$3$. Given a total of $120$ plants, the distribution is:
- Red $(RR)$: $1/4 \times 120 = 30$
- Pink $(Rr)$: $2/4 \times 120 = 60$
- White $(rr)$: $1/4 \times 120 = 30$
$4$. The intermediate color (pink) plants are $60$, and white plants are $30$. However, looking at the options provided, the question implies grouping the red and pink as 'colored' or 'intermediate'. Based on standard Mendelian ratios for incomplete dominance, $3/4$ of the population ($90$ plants) will show some color (Red + Pink) and $1/4$ ($30$ plants) will be white.

(C) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele, resulting in a third phenotype that is a blend of both parental traits.
In $Antirrhinum majus$ (snapdragon or dog flower), when a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$, the $F_1$ generation produces pink-flowered plants $(Rr)$.
This intermediate phenotype is a classic example of incomplete dominance.
$Pisum sativum$ (garden pea) follows the law of dominance as described by Mendel, where the dominant trait completely masks the recessive trait.

(B) In a standard monohybrid cross with complete dominance,the phenotypic ratio is $3:1$ and the genotypic ratio is $1:2:1$.
However,in cases of incomplete dominance (e.g.,flower color in $Antirrhinum$ $majus$ or snapdragon),the dominant allele does not completely mask the recessive allele.
As a result,the heterozygote shows an intermediate phenotype.
In the $F_2$ generation of such a cross,the phenotypic ratio becomes $1:2:1$ (one homozygous dominant,two heterozygous intermediate,and one homozygous recessive),which is identical to the genotypic ratio.

(D) In a typical Mendelian monohybrid cross,the $F_2$ phenotypic ratio is $3:1$ and the genotypic ratio is $1:2:1$.
However,in the case of incomplete dominance (e.g.,flower color in $Antirrhinum$ $majus$ or snapdragon),the dominant allele does not completely mask the recessive allele.
In the $F_2$ generation of an incomplete dominance cross,the phenotypic ratio is $1:2:1$ (Red:Pink:White) and the genotypic ratio is also $1:2:1$ $(RR:Rr:rr)$.
Thus,both ratios are identical in the $F_2$ generation.

(B) In snapdragon ($Antirrhinum$ $sp.$),the inheritance of flower color is an example of incomplete dominance.
Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele,resulting in an intermediate phenotype in the heterozygote.
Here,the $RR$ (red) genotype and $rr$ (white) genotype produce $Rr$ (pink) in the $F_1$ generation.
Upon selfing the $F_1$ $(Rr \times Rr)$,the $F_2$ generation shows a genotypic and phenotypic ratio of $1:2:1$ ($1$ $RR$ red : $2$ $Rr$ pink : $1$ $rr$ white),which is characteristic of incomplete dominance.

(A) The plant $Mirabilis$ $jalapa$ (Four o'clock plant) exhibits incomplete dominance,which is a deviation from Mendelian inheritance.
In $Mirabilis$ $jalapa$,when a red-flowered plant is crossed with a white-flowered plant,the $F_1$ generation produces pink flowers instead of red.
This phenomenon where the dominant allele does not completely mask the recessive allele is known as incomplete dominance.
$Pisum$ $sativum$ (Garden pea) was the organism used by Mendel for his experiments and follows Mendelian laws.
$Cicer$ $arietinum$ (Chickpea) and $Iberis$ $amara$ (Candytuft) generally follow Mendelian inheritance patterns.

(A) In $Mirabilis$ $jalapa$ (Four o'clock plant) and $Antirrhinum$ $majus$ (Snapdragon),the inheritance of flower color follows the pattern of incomplete dominance.
In this phenomenon,the dominant allele does not completely mask the expression of the recessive allele.
When a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$,the $F_1$ generation produces pink-flowered plants $(Rr)$.
This happens because the expression of the red color is not fully dominant over the white color,resulting in an intermediate phenotype (pink).

(D) This phenomenon is known as incomplete dominance,where neither allele is completely dominant over the other.
In $Mirabilis$ $jalapa$ (Four $O$'clock plant),the red flower gene $(R)$ and white flower gene $(r)$ show incomplete dominance.
Parental generation $(P)$: Red $(RR)$ $\times$ White $(rr)$
$F_1$ generation: All offspring are Pink $(Rr)$.
Selfing $F_1$ $(Rr \times Rr)$:
$F_2$ generation genotypes: $1 RR$ (Red) : $2 Rr$ (Pink) : $1 rr$ (White).
Thus,the phenotypic ratio is $1:2:1$.

(A) $Mirabilis \text{ jalapa}$ (Four o'clock plant) exhibits incomplete dominance for flower color.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$, the $F_1$ generation produces pink-flowered plants $(Rr)$.
When these $F_1$ pink-flowered plants are self-pollinated $(Rr \times Rr)$, the resulting $F_2$ generation shows a phenotypic ratio of $1$ Red $(RR)$ : $2$ Pink $(Rr)$ : $1$ White $(rr)$.
Thus, the phenotypic ratio is $1 : 2 : 1$.

(B) In incomplete dominance, the dominant allele does not completely mask the effect of the recessive allele.
As a result, the phenotype of the heterozygote $(Rr)$ is an intermediate blend of the two homozygous parents ($RR$ and $rr$).
In this specific case, the cross between red $(RR)$ and white $(rr)$ flowers results in pink $(Rr)$ offspring, which is a classic example of incomplete dominance observed in plants like $Mirabilis$ $jalapa$ (Four o'clock plant).

(C) In snapdragon (Antirrhinum majus),flower color inheritance exhibits incomplete dominance.
When a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$,the $F_1$ generation produces pink flowers $(Rr)$.
When these $F_1$ pink-flowered plants are self-crossed $(Rr \times Rr)$,the $F_2$ generation results in a phenotypic ratio of $1:2:1$ (Red:Pink:White),corresponding to the genotypes $1RR : 2Rr : 1rr$.
Therefore,the cross $Rr \times Rr$ produces all three varieties.

(B) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effects of the recessive allele,and the organism's resulting physical appearance shows a blending of both alleles. In this case,the $F_1$ generation phenotype is intermediate between the two parents. $A$ classic example is the flower color in $Antirrhinum$ $majus$ (Snapdragon or Dog flower),where a cross between red-flowered $(RR)$ and white-flowered $(rr)$ plants produces pink-flowered $(Rr)$ $F_1$ progeny.

(B) Gregor Mendel proposed the laws of inheritance based on his experiments with pea plants.
These include the Law of Dominance, the Law of Segregation, and the Law of Independent Assortment.
Incomplete dominance is a phenomenon where the dominant allele does not completely mask the recessive allele, resulting in an intermediate phenotype.
This was discovered by Carl Correns in $4 \text{ o'clock}$ plants $(Mirabilis \, jalapa)$ and was not proposed by Mendel.

(C) In incomplete dominance, the dominant allele does not completely mask the effect of the recessive allele.
In the case of $Mirabilis \text{ } jalapa$ (Four o'clock plant), when a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$, the $F_1$ generation produces pink flowers $(Rr)$.
When $F_1$ individuals are self-pollinated, the $F_2$ generation shows a phenotypic ratio of $1:2:1$ ($1$ Red : $2$ Pink : $1$ White).
This $1:2:1$ ratio is characteristic of incomplete dominance.

(A) This is a case of incomplete dominance where the grey phenotype is heterozygous $(Bb)$.
Let $B$ represent black and $b$ represent white.
The cross is $Bb \times Bb$,resulting in $1$ $BB$ (black) : $2$ $Bb$ (grey) : $1$ $bb$ (white).
Selfing the grey chickens $(Bb)$: The cross is $Bb \times Bb$,which results in $1$ $BB$ (black) : $2$ $Bb$ (grey) : $1$ $bb$ (white).
Selfing the black chickens $(BB)$: The cross is $BB \times BB$,which results in all $BB$ (black) offspring.
Since the question asks for the phenotype of the offspring produced by selfing the grey chickens and the black chickens separately,the grey selfing produces a ratio of $1:2:1$ (black:grey:white),while the black selfing produces all black offspring. Given the options,the question implies the result of selfing the grey chickens,which is $1$ $BB$ (black) : $2$ $Bb$ (grey) : $1$ $bb$ (white). However,if we look at the specific progeny mentioned,selfing grey $(Bb)$ results in $25\%$ black,$50\%$ grey,and $25\%$ white. If the question implies the result of selfing the black chickens $(BB)$,they are homozygous and will produce all black offspring.

(C) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele, resulting in a phenotype that is a blend of both parents.
In $Antirrhinum$ $majus$ (Snapdragon or Dog flower), when a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$, the $F_1$ generation produces pink-flowered plants $(Rr)$.
This intermediate phenotype clearly demonstrates that neither allele is completely dominant over the other, making it the classic example of incomplete dominance.

(D) In Snapdragon $(Antirrhinum \text{ } sp.)$, the inheritance of flower color exhibits $Incomplete \text{ } Dominance$.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$, the $F_1$ generation produces heterozygous plants $(Rr)$.
Due to incomplete dominance, the dominant allele $(R)$ is unable to completely mask the expression of the recessive allele $(r)$.
As a result, the phenotype of the $F_1$ hybrid is intermediate between the two parents, which is pink.

(B) In the dog flower (Antirrhinum majus),the inheritance of flower color exhibits incomplete dominance.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$,the $F_1$ generation results in plants with pink flowers $(Rr)$.
The pink color is an intermediate phenotype that is not similar to either the red parent or the white parent.
Therefore,the $F_1$ phenotype does not resemble either of the two parents.

(B) In $Mendelian$ genetics, a cross between two homozygous parents (Red $RR$ and White $rr$) results in an $F_1$ generation that is heterozygous $(Rr)$.
When this $F_1$ generation undergoes self-pollination, the $F_2$ generation typically shows a $3:1$ phenotypic ratio if complete dominance is present.
However, if the phenotypic ratio is $1:2:1$ (e.g., $1$ Red : $2$ Pink : $1$ White), it indicates that the dominant allele is not fully masking the recessive allele.
This phenomenon is known as $Incomplete$ $dominance$, where the heterozygote shows an intermediate phenotype between the two homozygous parents.

(B) This is an example of incomplete dominance.
Parental genotypes: White $(rr)$ $\times$ Pink $(Rr)$.
Gametes produced by White parent: $(r)$.
Gametes produced by Pink parent: $(R)$ and $(r)$.
Crossing these gametes results in the following offspring genotypes:
$r \times R = Rr$ (Pink)
$r \times r = rr$ (White)
The resulting phenotypic ratio is $1$ Pink : $1$ White,which is $(1 : 1)$.

(D) अपूर्ण प्रभाविता वह घटना है जिसमें विषमयुग्मजी संतति में दोनों एलील का प्रभाव मिश्रित हो जाता है और कोई भी एलील पूरी तरह से प्रभावी नहीं होता है। $Mirabilis jalapa$ (फोर ओ क्लॉक प्लांट) और $Antirrhinum majus$ (स्नैपड्रैगन) में पुष्प के रंग में अपूर्ण प्रभाविता देखी जाती है। इसके अतिरिक्त, एंडालुसियन फाउल (मुर्गी की एक नस्ल) में भी पंखों के रंग में अपूर्ण प्रभाविता देखी जाती है। अतः, सही उत्तर $D$ है।

(D) : The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum $sp.$) is a good example which shows incomplete dominance.
In a cross between true-breeding red-flowered $(RR)$ and true-breeding white-flowered plants $(rr)$,the $F_1$ $(Rr)$ was pink.
When the $F_1$ was self-pollinated,the $F_2$ resulted in the following ratio: $1$ $(RR)$ Red : $2$ $(Rr)$ Pink : $1$ $(rr)$ White.
Here,the genotype ratios were $1 : 2 : 1$,as in any Mendelian monohybrid cross,but the phenotype ratios had changed from the $3 : 1$ dominant:recessive ratio to $1 : 2 : 1$.

(C) The given situation is an example of incomplete dominance,where the phenotype in the $F_1$ generation does not resemble either of the two parents.
In $Antirrhinum$ (snapdragon),the cross between a red-flowered plant $(RR)$ and a white-flowered plant $(rr)$ results in pink-flowered plants $(Rr)$ in the $F_1$ generation.
When two pink-flowered plants $(Rr)$ are hybridized,the cross is $Rr \times Rr$.
The resulting offspring genotypes are $1 RR$ (red) : $2 Rr$ (pink) : $1 rr$ (white).
Therefore,the genotype of the two plants used for hybridization is $Rr$.

(B) In $Antirrhinum$ $majus$ (snapdragon),the inheritance of flower color follows the pattern of incomplete dominance.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$,the $F_1$ generation consists of plants with pink flowers $(Rr)$.
This occurs because the dominant allele $(R)$ is not completely dominant over the recessive allele $(r)$,resulting in an intermediate phenotype in the heterozygote.
Therefore,this phenomenon is known as incomplete dominance.

(A) In snapdragon ($Antirrhinum$ $sp.$),flower color inheritance exhibits incomplete dominance.
When a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$,the $F_1$ generation produces pink-flowered plants $(Rr)$.
When $F_1$ plants $(Rr)$ are self-pollinated,the $F_2$ generation results in the following genotypes: $1$ $RR$ (red) : $2$ $Rr$ (pink) : $1$ $rr$ (white).
Thus,the phenotypic ratio in the $F_2$ generation is $1:2:1$.

(D) In snapdragon ($Antirrhinum$ $majus$),the inheritance of flower color exhibits incomplete dominance.
When a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$,the $F_1$ generation produces plants with the genotype $Rr$.
Due to incomplete dominance,the dominant allele $(R)$ is unable to completely mask the expression of the recessive allele $(r)$.
As a result,the $F_1$ hybrids exhibit an intermediate phenotype,which is pink.

(D) In incomplete dominance, the dominant allele does not completely mask the recessive allele.
As a result, the heterozygous phenotype is an intermediate between the two homozygous phenotypes.
For example, in $Mirabilis jalapa$ (four-o'clock plant), a cross between red $(RR)$ and white $(rr)$ flowers results in pink $(Rr)$ flowers in the $F_1$ generation.
When $F_1$ hybrids $(Rr)$ are self-pollinated, the $F_2$ generation shows a phenotypic ratio of $1$ (red) : $2$ (pink) : $1$ (white).
The genotypic ratio is also $1$ $(RR)$ : $2$ $(Rr)$ : $1$ $(rr)$.
Therefore, both the phenotypic and genotypic ratios are $1:2:1$.

(B) In Mendelian genetics, complete dominance typically results in a phenotypic ratio of $3:1$ and a genotypic ratio of $1:2:1$ in the $F_2$ generation.
However, in cases of Incomplete dominance, the dominant allele does not completely mask the recessive allele.
As a result, the heterozygote shows an intermediate phenotype.
For example, in $Mirabilis$ \text{ jalapa} (Four o'clock plant), a cross between red and white flowers produces pink flowers in the $F_1$ generation.
When $F_1$ plants are self-pollinated, the $F_2$ generation shows a phenotypic ratio of $1$ (Red) $: 2$ (Pink) $: 1$ (White) and a genotypic ratio of $1 (RR) : 2 (Rr) : 1 (rr)$.
Thus, both the genotypic and phenotypic ratios are identical $(1:2:1)$.

(B) In $Antirrhinum$ (snapdragon),the inheritance of flower color shows incomplete dominance.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(WW)$,the $F_1$ generation produces pink-flowered plants $(RW)$.
This occurs because the dominant allele $(R)$ is not completely dominant over the recessive allele $(W)$,resulting in an intermediate phenotype (pink) in the heterozygote.

(D) In a standard Mendelian monohybrid cross with complete dominance,the phenotypic ratio is $3:1$ and the genotypic ratio is $1:2:1$.
However,in cases of incomplete dominance (e.g.,in $Antirrhinum$ $majus$ or snapdragon),the dominant allele does not completely mask the recessive allele.
As a result,the heterozygotes show an intermediate phenotype.
Therefore,in the $F_2$ generation of an incomplete dominance cross,the phenotypic ratio becomes $1:2:1$ ($1$ red : $2$ pink : $1$ white),which is identical to the genotypic ratio $(1:2:1)$.

(D) In $Antirrhinum$ (Snapdragon),the inheritance of flower colour is an example of incomplete dominance.
$1$. The Principle of Dominance states that one allele masks the expression of another,which is not observed here as the phenotype is intermediate (pink).
$2$. Incomplete dominance results in a phenotypic ratio of $1:2:1$ ($1$ Red : $2$ Pink : $1$ White) in the $F_{2}$ generation,which matches the genotypic ratio.
$3$. The Law of Segregation (Mendel's First Law) states that alleles separate during gamete formation. This law is universal and applies to all sexually reproducing organisms,including $Antirrhinum$. Therefore,the statement that the Law of Segregation does not apply is incorrect.

(A) In $Mirabilis$ $jalapa$ (four o'clock plant),flower colour exhibits incomplete dominance.
When $F_1$ pink flowered plants $(Rr)$ are selfed,the $F_2$ generation results in a phenotypic and genotypic ratio of $1:2:1$.
The ratio is as follows:
$1$ $RR$ (Red) : $2$ $Rr$ (Pink) : $1$ $rr$ (White).
Since both the phenotypic ratio ($1$ Red : $2$ Pink : $1$ White) and the genotypic ratio ($1$ $RR$ : $2$ $Rr$ : $1$ $rr$) are identical $(1:2:1)$,the Assertion is correct.
This occurs specifically because the gene for flower colour shows incomplete dominance,making the Reason the correct explanation for the Assertion.

(N/A) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the expression of the recessive allele,resulting in a phenotype that is intermediate between the two homozygous parents.
When experiments on peas were repeated using other traits in other plants,it was found that sometimes the $F_{1}$ generation had a phenotype that did not resemble either of the two parents and was intermediate between the two.
The inheritance of flower colour in the dog flower (Snapdragon or Antirrhinum sp.) is a classic example to understand incomplete dominance.
In a cross between true-breeding red-flowered $(RR)$ and true-breeding white-flowered $(rr)$ plants,the $F_{1}$ $(Rr)$ generation was pink.
When the $F_{1}$ plants were self-pollinated,the $F_{2}$ generation resulted in the following ratio: $1$ $(RR)$ Red : $2$ $(Rr)$ Pink : $1$ $(rr)$ White.
Here,the genotypic ratios were exactly as expected in any Mendelian monohybrid cross $(1:2:1)$,but the phenotypic ratio had changed from the typical $3:1$ dominant:recessive ratio to $1:2:1$.
This occurs because the '$R$' allele is not completely dominant over the '$r$' allele,making it possible to distinguish the heterozygous $Rr$ (pink) from the homozygous $RR$ (red) and $rr$ (white).

(N/A) When the $F_2$ generation of a monohybrid cross exhibits identical genotypic and phenotypic ratios,it indicates the phenomenon of incomplete dominance.
In incomplete dominance,neither of the two alleles is completely dominant over the other.
As a result,the heterozygote $(Rr)$ expresses an intermediate phenotype,distinct from both the homozygous dominant $(RR)$ and homozygous recessive $(rr)$ parents.
For example,in snapdragon plants,the cross between red-flowered $(RR)$ and white-flowered $(rr)$ plants results in pink-flowered $(Rr)$ plants in the $F_1$ generation.
Upon selfing the $F_1$ generation,the $F_2$ generation shows:
Phenotypic ratio $\rightarrow$ Red : Pink : White = $1:2:1$
Genotypic ratio $\rightarrow$ $RR : Rr : rr = 1:2:1$
Since both ratios are $1:2:1$,it confirms that the alleles show incomplete dominance.