Incomplete dominance Questions in English

(N/A) This phenomenon is known as incomplete dominance. In this case,the $F_1$ generation does not resemble either of the two parents; instead,it exhibits an intermediate phenotype (orange) that is a blend of the two parental traits (red and yellow). This occurs because neither allele is completely dominant over the other,resulting in the expression of an intermediate trait in the heterozygous condition.

(C) In a standard Mendelian monohybrid cross,the phenotypic ratio is $3:1$ and the genotypic ratio is $1:2:1$.
In the case of incomplete dominance (e.g.,in $Antirrhinum$ $majus$ or snapdragon),the phenotypic ratio of the $F_2$ generation is $1:2:1$ (red:pink:white).
The genotypic ratio in incomplete dominance is also $1:2:1$ (homozygous dominant:heterozygous:homozygous recessive).
However,the question asks for a phenomenon that follows the Mendelian phenotypic ratio $(3:1)$ but deviates from the genotypic ratio.
Actually,incomplete dominance is characterized by the phenotypic ratio becoming $1:2:1$,which matches the genotypic ratio.
Therefore,the correct answer is $C$.

(C) In incomplete dominance,the dominant allele does not completely mask the effect of the recessive allele.
In $Antirrhinum$ $majus$ (Snapdragon),when a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$,the $F_1$ generation produces pink-flowered plants $(Rr)$.
When these $F_1$ pink-flowered plants $(Rr)$ are self-pollinated to obtain the $F_2$ generation,the resulting phenotypic ratio is $1$ (Red) : $2$ (Pink) : $1$ (White).
Thus,the phenotypic ratio in the $F_2$ generation is $1 : 2 : 1$,which is identical to the genotypic ratio.

(A) In incomplete dominance,the cross between two heterozygous parents $(Rr \times Rr)$ results in an $F_2$ generation with a genotypic ratio of $1RR : 2Rr : 1rr$.
Here,$RR$ represents the homozygous dominant phenotype,$Rr$ represents the intermediate phenotype (heterozygous),and $rr$ represents the homozygous recessive phenotype.
The total number of parts in the ratio is $1 + 2 + 1 = 4$.
The proportion of the $Rr$ genotype is $2/4$,which simplifies to $1/2$ or $50 \%$.

(B) In pea plants, the gene for starch synthesis has two alleles, $B$ and $b$.
$BB$ homozygotes produce large starch grains, while $bb$ homozygotes produce small starch grains.
However, the $Bb$ heterozygotes produce intermediate-sized starch grains.
Since the phenotype of the heterozygote is intermediate between the two homozygous phenotypes, this is an example of $Incomplete \text{ } dominance$.

(B) The inheritance of flower color in $Snapdragon$ ($Antirrhinum$ $sp.$) exhibits $Incomplete$ $dominance$, where the $F_1$ generation shows an intermediate phenotype (pink) instead of the dominant trait (red). This deviates from the Mendelian principle of $Dominance$, where the $F_1$ hybrid usually resembles the dominant parent. Therefore, $Snapdragon$ is the correct answer.

(C) In $Incomplete \text{ } dominance$, the $F_1$ generation does not resemble either of the two parents and is in between the two.
In this phenomenon, the dominant allele does not completely mask the effect of the recessive allele, resulting in 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.

(C) In $Mirabilis \text{ } jalapa$ (Four O'clock plant), when a red-flowered plant $(RR)$ is crossed with a white-flowered plant $(rr)$, the $F_1$ generation produces pink-flowered plants $(Rr)$.
This happens because the dominant allele is not completely dominant over the recessive allele, resulting in an intermediate phenotype.
This phenomenon is known as incomplete dominance.

(B) स्नैपड्रैगन (एंटीराइनम प्रजाति) में अपूर्ण प्रभाविता (Incomplete dominance) देखी जाती है।
जब लाल पुष्प वाले पौधे $(RR)$ और सफेद पुष्प वाले पौधे $(rr)$ के बीच संकरण कराया जाता है,तो $F_1$ पीढ़ी में सभी पौधे गुलाबी पुष्प $(Rr)$ वाले प्राप्त होते हैं।
जब $F_1$ पीढ़ी के पौधों का स्व-परागण कराया जाता है,तो $F_2$ पीढ़ी में जीनप्ररूपी अनुपात $RR : Rr : rr$ यानी $1:2:1$ प्राप्त होता है।
अपूर्ण प्रभाविता में,लक्षणप्ररूपी अनुपात (phenotypic ratio) भी जीनप्ररूपी अनुपात के समान ही $1:2:1$ (लाल : गुलाबी : सफेद) होता है।

(A) In incomplete dominance,the heterozygous offspring exhibit a phenotype that is intermediate between the two homozygous parents.
In the $F_2$ generation obtained by self-pollination of the $F_1$ generation,the phenotypic ratio is $1:2:1$ (e.g.,Red : Pink : White).
Similarly,the genotypic ratio is also $1:2:1$ (e.g.,$RR : Rr : rr$).
Therefore,in incomplete dominance,the genotypic and phenotypic ratios in the $F_2$ generation are identical $(1:2:1)$.

(C) In incomplete dominance,the dominant allele does not completely mask the recessive allele.
In $Antirrhinum$ (snapdragon),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 the following genotypes: $1 RR$ (red) : $2 Rr$ (pink) : $1 rr$ (white).
Thus,the phenotypic ratio of red,pink,and white flowers is $1 : 2 : 1$.
Since the question asks for the ratio of pink,red,and white flowers respectively,the ratio remains $2 : 1 : 1$ based on the order provided in the question.

(D) 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 an intermediate of the two parents.
$Mirabilis$ $jalapa$ (Four o'clock plant) and $Antirrhinum$ $majus$ (Snapdragon/Dog flower) are classic examples of incomplete dominance.
Since both $Mirabilis$ $jalapa$ and $Antirrhinum$ $majus$ (which is the scientific name for Snapdragon/Dog flower) exhibit incomplete dominance, none of the given options represent a plant that does not show this trait.
Therefore, the correct answer is $D$.

(D) In incomplete dominance,the pink flower is the intermediate phenotype resulting from the heterozygous condition $(Rr)$.
When we cross a homozygous red flower $(RR)$ with a homozygous white flower $(rr)$:
$RR \times rr \rightarrow Rr$ (Pink).
In this cross,$100\%$ of the progeny are pink $(Rr)$.
In contrast,a cross between two pink flowers $(Rr \times Rr)$ results in a phenotypic ratio of $1:2:1$ (Red:Pink:White),where only $50\%$ of the offspring are pink. Therefore,the cross between red and white produces the highest proportion of pink flowers.

(B) Mirabilis jalapa exhibits incomplete dominance,where the heterozygous condition $(Rr)$ results in a pink phenotype instead of red.
When a pink-flowered plant $(Rr)$ is crossed with a white-flowered plant $(rr)$,the gametes produced by the pink plant are $R$ and $r$,while the white plant produces only $r$ gametes.
The resulting offspring genotypes are $Rr$ (pink) and $rr$ (white) in a $1: 1$ ratio.
Therefore,the expected phenotypic ratio is $1$ pink : $1$ white.

(C) Intermediate inheritance,also known as incomplete dominance,is a phenomenon where the phenotypic and genotypic ratios in the $F_2$ generation are identical,both being $1:2:1$.
In this type of inheritance,the dominant allele does not completely mask the recessive allele,resulting in an intermediate phenotype in the heterozygote.
Classic examples include the four o'clock plant $(Mirabilis \ jalapa)$ and snapdragon $(Antirrhinum \ majus)$.

(B) In garden pea,the gene for seed shape ($B$ for round and $b$ for wrinkled) also controls starch synthesis.
$BB$ (homozygous round) plants produce large starch grains and are round.
$bb$ (wrinkled) plants produce small starch grains and are wrinkled.
$Bb$ (heterozygous) plants produce intermediate-sized starch grains and appear round.
Since $BB$ plants produce the largest starch grains,starch is synthesised most effectively in homozygous round seeded plants.

(D) In Antirrhinum (snapdragon),flower color exhibits incomplete dominance.
Genotype $RR$ produces red flowers,$rr$ produces white flowers,and the heterozygous genotype $Rr$ produces pink flowers.
$A$ test cross involves crossing an individual with a recessive parent. Here,the recessive parent is white-flowered $(rr)$.
The cross is: Pink $(Rr)$ $\times$ White $(rr)$.
The gametes produced by $Rr$ are $R$ and $r$,and by $rr$ is $r$.
The resulting progenies are:
$Rr$ (Pink) and $rr$ (White).
Thus,the phenotypic ratio is $1 \text{ Pink} : 1 \text{ White}$.

(D) In incomplete dominance,the dominant allele does not completely mask the effect of the recessive allele.
As a result,the $F_{1}$ generation exhibits a phenotype that is an intermediate blend of the two parental traits.
For example,in $Antirrhinum$ $majus$ (snapdragon),a cross between red $(RR)$ and white $(rr)$ flowers results in pink $(Rr)$ flowers in the $F_{1}$ generation.
In the $F_{2}$ generation,the genotypic ratio is $1:2:1$ $(RR:Rr:rr)$ and the phenotypic ratio is also $1:2:1$ (Red:Pink:White).
Therefore,the phenotypic and genotypic ratios are identical in incomplete dominance,which contradicts option $B$.
However,looking at the options provided,option $D$ is the most accurate description because the $F_{1}$ phenotype is an intermediate expression resulting from the influence of both alleles.

(A) In snapdragon $(Antirrhinum \, sp.)$, the inheritance of flower color shows incomplete dominance.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$, the $F_{1}$ generation produces pink-flowered plants $(Rr)$.
This happens because neither of the two alleles is completely dominant over the other, resulting in an intermediate phenotype.
Therefore, both the Assertion and the Reason are correct, and the Reason is the correct explanation of the Assertion.

(C) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effects of the recessive allele, resulting in a phenotype that is a blend of both parents.
In the case of $Mirabilis$ $jalapa$ (Four o'clock plant), when a pure red-flowered plant $(RR)$ is crossed with a pure white-flowered plant $(rr)$, the $F_1$ generation produces pink-flowered plants $(Rr)$.
This intermediate phenotype indicates that neither allele is completely dominant over the other, which is the definition of incomplete dominance.

(B) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the recessive allele,resulting in an intermediate phenotype in the heterozygote.
For a monohybrid cross involving incomplete dominance (e.g.,flower color in Mirabilis jalapa),the $F_2$ generation shows both phenotypic and genotypic ratios as $1: 2: 1$.
- The phenotypic ratio is $1$ (Red) : $2$ (Pink) : $1$ (White) = $1: 2: 1$.
- The genotypic ratio is $1$ $(RR)$ : $2$ $(Rr)$ : $1$ $(rr)$ = $1: 2: 1$.
Therefore,both $P$ and $Q$ are $1: 2: 1$.

(B) In Mendel's monohybrid cross,the phenotypic ratio is $3:1$ and the genotypic ratio is $1:2:1$.
In incomplete dominance (e.g.,in $Antirrhinum$ $majus$),the phenotypic ratio is $1:2:1$ and the genotypic ratio is $1:2:1$.
Since the phenotypic ratio in incomplete dominance $(1:2:1)$ differs from the phenotypic ratio in Mendel's monohybrid cross $(3:1)$,the phenotypic ratio does not match.

(B) The given experiment shows a cross between red-flowered $(RR)$ and white-flowered $(rr)$ plants of $Antirrhinum$ $sp.$ (Snapdragon).
In the $F_1$ generation,all plants are pink $(Rr)$,which is an intermediate phenotype between red and white.
In the $F_2$ generation,the phenotypic ratio is $1:2:1$ (Red:Pink:White),which is identical to the genotypic ratio.
This phenomenon,where the dominant allele does not completely mask the recessive allele,resulting in an intermediate phenotype,is known as Incomplete dominance.

(C) In pea plants,the gene controlling starch synthesis has two alleles,$B$ and $b$.
$BB$ homozygotes produce large starch grains,while $bb$ homozygotes produce small starch grains.
However,the heterozygotes $(Bb)$ produce starch grains of intermediate size.
Since the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes,this is an example of incomplete dominance.

(A) In Snapdragon $(Antirrhinum \text{ } majus)$, flower color exhibits incomplete dominance. The genotype for red flowers is $RR$, white flowers is $rr$, and pink flowers is $Rr$.

Gametes	$R$	$r$
$R$	$RR$ (Red)	$Rr$ (Pink)
$R$	$RR$ (Red)	$Rr$ (Pink)

The resulting progeny genotypes are $50\% \text{ } RR$ (Red) and $50\% \text{ } Rr$ (Pink).
Therefore, the expected phenotypes in the progeny are red flowered and pink flowered plants.

(D) In $Pisum$ $sativum$ (pea plant),the size of starch grains is controlled by a single gene with two alleles ($B$ and $b$).
$BB$ homozygotes produce large starch grains,while $bb$ homozygotes produce small starch grains.
When these are crossed,the $F_1$ heterozygotes $(Bb)$ produce starch grains of intermediate size.
This phenomenon is an example of incomplete dominance,where the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygous parents.

(A) The correct answer is $A$.
Incomplete dominance is a phenomenon in which the $F_1$ phenotype is intermediate between the two parental phenotypes,rather than one allele completely masking the other.
Option $A$ describes the definition of complete dominance,not incomplete dominance.
Option $B$ is correct as snapdragon exhibits incomplete dominance,resulting in pink flowers in the $F_1$ generation.
Option $C$ is the correct definition of dominance.
Option $D$ is correct because recessive alleles often code for non-functional enzymes or no enzyme,leading to the recessive trait.

(B) The genotype $(Bb)$ in pea plants exhibits the phenomenon of incomplete dominance regarding starch grain size.
While the shape of the seed is controlled by the gene $B$ (where $B$ is dominant for round and $b$ is recessive for wrinkled),the size of the starch grains is controlled by the same gene.
In the homozygous condition,$BB$ produces large starch grains,and $bb$ produces small starch grains.
In the heterozygous condition $(Bb)$,the starch grains are of intermediate size.
Therefore,the genotype $(Bb)$ results in round seeds with intermediate-sized starch grains.

(B) The inheritance of starch grain size in pea plants is an example of incomplete dominance.
Let $B$ represent the allele for large starch grains and $b$ represent the allele for small starch grains.
The genotype $BB$ produces large starch grains,$bb$ produces small starch grains,and the heterozygous genotype $Bb$ produces intermediate sized starch grains.
When both parents are heterozygous $(Bb \times Bb)$,the phenotypic ratio of the progeny is $1:2:1$ $(BB:Bb:bb)$.
Here,$25\%$ of the progeny will be $BB$ (large),$50\%$ will be $Bb$ (intermediate),and $25\%$ will be $bb$ (small).
Therefore,$50\%$ of the progeny will have intermediate sized starch grains.

(C) 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.
In snapdragon ($Antirrhinum$ $sp.$),the cross between red $(RR)$ and white $(rr)$ flowers produces pink $(Rr)$ flowers in the $F_1$ generation.
When two pink $(Rr)$ plants are crossed,the $F_2$ generation shows a phenotypic ratio of $1$ Red $(RR)$ : $2$ Pink $(Rr)$ : $1$ White $(rr)$.
Therefore,option $C$ is incorrect because crossing two pink flowered plants results in red,pink,and white flowered plants,not only red flowered plants.

(C) In incomplete dominance,a cross between two homozygous parents (e.g.,Red $RR$ and White $rr$) results in a heterozygous $F_1$ generation with an intermediate phenotype (Pink $Rr$).
When the $F_1$ generation $(Rr)$ is self-crossed,the $F_2$ generation shows a phenotypic ratio of $1:2:1$ (Red:Pink:White).
From the Punnett square:
- Red $(RR)$: $1/4$ or $25\%$
- Pink $(Rr)$: $2/4$ or $50\%$
- White $(rr)$: $1/4$ or $25\%$
Thus,each of the parental traits (Red and White) reappears in the $F_2$ generation with a frequency of $25\%$.

(A) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effect of the recessive allele.
As a result, the heterozygous offspring exhibit an intermediate phenotype that is a blend of the two parental traits.
In this case, the cross between red $(RR)$ and white $(rr)$ flowers results in pink $(Rr)$ flowers, which is a classic example of incomplete dominance, commonly observed in plants like $Mirabilis$ \text{ } $jalapa$ (Four o'clock plant).

(D) In $Mirabilis$ $jalapa$ (Four $O$'clock plant),the inheritance of flower color exhibits incomplete dominance.
When a homozygous red-flowered plant $(RR)$ is crossed with a homozygous white-flowered plant $(rr)$,all the $F_1$ hybrid offspring have the genotype $Rr$.
Due to incomplete dominance,the $Rr$ genotype results in a pink phenotype rather than red or white.
Therefore,$100\%$ of the $F_1$ hybrids obtained from this cross will be pink.

(A) Incomplete dominance is a phenomenon where the dominant allele does not completely mask the effects of the recessive allele, resulting in an intermediate phenotype in the heterozygote.
In the Dog flower plant $(Antirrhinum \text{ } majus)$, the cross between a red-flowered plant $(RR)$ and a white-flowered plant $(rr)$ results in pink-flowered offspring $(Rr)$ in the $F_1$ generation.
This intermediate pink colour demonstrates incomplete dominance, as neither the red nor the white trait is completely dominant over the other.

(B) The correct answer is $B$ $(1:2:1)$.
In incomplete dominance,the phenotypic and genotypic ratios are identical.
For a cross between two heterozygous individuals (e.g.,$Rr \times Rr$),the resulting offspring follow the ratio $1$ (homozygous dominant) : $2$ (heterozygous) : $1$ (homozygous recessive).
Thus,the genotypic ratio is $1:2:1$.