Incomplete dominance - class-X
Description: incomplete dominance | |
Number of Questions: 46 | |
Created by: Sanjiv Memon | |
Tags: classical genetics inheritance botany biology |
Phenotypic and genotypic ratio is similar in case of?
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Complete dominance
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Incomplete dominance
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Over dominance
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Epistasis
The segregration of alleles is a random process and so there is a _______ chance of a gametes containing either allele.
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$25\%$
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$50\%$
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$75\%$
-
$100\%$
According to Mendel"s law of segregation, alleles segregate from one another so that the gametes will have only one copy of the particular gene. In a diploid organism, there are two alleles for a particular gene, which segregate and only one of each allele can be present in a gamete, therefore, since there are two alleles for a gene, chances of a gamete containing either of the allele is 50%.
When the phenotypic and genotypic ratios resemble in the F$ _2$ generation, it is an example of
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Independent assortment
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Qualitative inheritance
-
Segregation of factors
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Incomplete dominance
Incomplete dominance: It is a type of intragenic (or interallellic) interaction where both the alleles of a given trait express as a blend (mixture) as against a normal Mendelian pattern where one allele is dominant over the other. As a resulting of this blending, an intermediate character is expressed. This situation occurs due to the fact that the dominant gene is not in a position to completely suppress the expression of recessive gene. With the result, the heterozygous offspring will be phenotypically and genotypically different from either of the homozygous parent.
When a hybrid plant with pink (Rr) flower of Mirabilis is crossed with white flower, the expected phenotype ratio is
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red : pink : white, 1 : 2 : 1
-
pink : white, 1 : 1
-
red : pink, 1 : 1
-
red : white, 3 : 1
Hybrid - Rr pink flower and white flower - rr
Genotypes: Rr x rr
Gametes: R, r r
Offspring: Rr, rr
The ratio of pink flower: white flower = 1:1
RR(red) is crossed with rr (white). All Rr offsprings are pink. This indicates that R gene is
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Hybrid
-
Incompletely dominant
-
Recessive
-
Mutant
Incomplete dominance refers to a genetic situation in which one allele does not completely dominate another allele and, therefore, results in a new phenotype. It shows that the dominant allele is incompletely dominant.
Examples of incomplete dominance are:
2. A brown fur coat on a rabbit as a result of one rabbit's red allele and one rabbit's white allele not dominating.
Which one of the following represents a deviation from Mendelian concepts?
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Segregation
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Independent assessment
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Purity of gametes
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Incomplete dominance
Incomplete dominance is the only option which does not obey Mendel's principles. Mendel postulated law of segregation, independent assortment, dominance, purity of gametes, etc. According to Mendel's theories, the alleles constituting the genes will separate and segregate during meiosis for the formation of gametes. It produces the expression of either dominant or recessive - dominant expresses in both homo and heterozygous conditions, recessive expresses only in homozygous condition. But incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a third phenotype in which the expresses physical trait is a combination of the dominant and recessive phenotypes.
If in snapdragon, a homozygous dominant red-flowered plant is crossed with a homozygous recessive white flowered plant, the offspring would be
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Half red-flowered
-
Half white-flowered
-
All red-flowered
-
Pink-flowered
Homozygous dominant red flowered plant- RR
Homozygous recessive white flowered plant- rr
Genotypes: RR x rr
Gametes: R r
F$ _{1}$: Rr (pink-coloured flower)
This is an example of incomplete dominance.
In Mirabilis, red (RR) and white (rr) flower produces pink (Rr) flower. A plant with pink flower is crossed with a white flower the expected phenotypic ratio is
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Red : pink : white (1 : 2: 1)
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Pink : white (1 :1)
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Red : pink (1 : 1)
-
Red : white (3:1)
Red flower plant fuses with white flower plant.
Genotype : Red (RR) x White (rr)
Gametes : R r
| | R | r | | --- | --- | --- | | r | Rr | rr | | r | Rr | rr |
In Mirabilis jalapa when homozygous red flowered and white flowered plants are crossed, all F$ _1$ plants have pink coloured flowers. In F$ _2$ produced by selfing of F$ _1$ plants, red, pink, white flowered plants would appear respectively in the ratio of
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1:1:2
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2:1:1
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1:0:1
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1:2:1
In the plant Mirabilis jalapa, commonly called as four o'clock plant, the inheritance of flower colour is an example for incomplete dominance. The plant produces two types of flowers red coloured and white coloured. This condition is an example for a pair of contrasting characters. When a plant which is homozygous for red flowers (AA) is crossed with a plant which is homozygous for white flowers (aa), the plants of the F$ _{1}$ generation produce pink flowers which is a blend of red and white condition. This result clearly indicates that neither red flowered condition nor white flowered condition is dominant. However, when two hybrid plants with pink flowers (Aa) are crossed, the F$ _{2}$ generation plants show red flowered, pink flowered and white flowered condition in the ratio 1:2:1. This ratio is very much in accordance with the law of segregation.
This example very clearly indicates
1. The phenomenon of incomplete dominance
2. That the genes responsible for red and white flowers do not actually mix, since both the pure characters reappear in the F$ _{2}$ generation
3. That there is no specific gene responsible for producing pink flowers
4. That the homozygous white flowered plants have genes aa which is unable to produce the colouring pigment
5. That the heterozygous pink flowered plants have genes Aa and hence can produce only half the amount of colouring pigment that is normally produced in a red flowered plant (AA).
Which cross yields red, white and pink flowers variety of dog flower?
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RR $\times$ Rr
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Rr $\times$ RR
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Rr $\times$ Rr
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Rr $\times$ rr
The F1-hybrid plants have a different phenotype (pink flowers) than either of the true-breeding parents. This is an example of incomplete dominance. When the F1-hybrid plants are self-fertilized, both parental phenotypes (red flowered plants and white flowered plants) reappear in the F2 generation.
The phenomenon of incomplete dominance was observed by
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Hugo de vries
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Correns
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Tschermak
-
None of the above
Even though Mendel did not try to explain traits that did blend, other scientists eventually did. The discovery of incomplete dominance is usually credited to German Botanist Carl Correns who studied four o'clock plants. Instead of having only two colors of petals on the flowers, there was an intermediate colour that would show up that corresponded to Mendel's genotype ratio of 1:2:1 instead of his pheontype ratio of 3:1. This showed that each genotype corresponded to its own unique phenotype and that the heterozygotes were showing a blend of both alleles instead of one being completely dominant over the other.
Incomplete dominance was actually seen and recorded long before Carl Correns published his works and even before Gregor Mendel worked with his pea plants and published his findings. Since there was no discipline known as Genetics at that time, however, it was not fully explored. Scientists dating back to ancient times discussed the blending of traits in their writings which could be attributed to incomplete dominance. However, it wasn't until after Mendel and Correns that the term "incomplete dominance" came into common usage and the mechanism for how it worked was known.
In incomplete dominance, ratio of red: pink: white is
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1:2:1
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1:1:2
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1:2:2
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2:2:1
Incomplete Dominance is the blending of alleles to create a phenotype that is a combination of both traits the alleles code for. Incomplete dominance is a type of non-Mendelian genetics.
Complete dominance does not occur in
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Mirabilis jalapa
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Oenothera lamarckiana
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Lathyrus odoratus
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All of the above
As we know that trait is represented by two contrasting factors of a gene in a heterozygous individual; the allele/factor that can express itself in the heterozygous individual is called as the dominant trait. The other factor, whose effect is masked by the presence of dominant factor, is called recessive factor. In the case of complete dominance, the heterozygous individual shows dominant phenotype. Law of incomplete dominance tells that where none of the factors of a gene is dominant, the phenotype of the heterozygous dominant individual is the blend of dominant and recessive traits. For example, flower colour in Mirabilis jalapa and sweet peas (Lathyrus odoratus) shows incomplete dominance and the monohybrid cross between two pure varieties gives 1:2:1 phenotypic ratio in F$ _2$ generation which is 3:1 in dominant traits. Monohybrid cross in Oenothera lamarckiana does not give typical 3:1 ratio, hence does not follow complete dominance. Pisum sativum was the experimental plant of Mendel and show complete dominance.
The $F _2$ phenotypic ratio of 1 : 2 : 1 is obtained in those crosses that exhibit
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Complete dominanc
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Partial dominance
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Co-dominance
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Both B and C
Partial dominance | R | r |
---|---|---|
R | RR (red) | Rr (pink) |
r | Rr (pink) | rr (white) |
Co-dominance | A | B |
---|---|---|
A | AA (A blood group) | AB (AB blood group) |
B | AB (AB blood group) | BB (B blood group) |
Partial dominance is also known as incomplete dominance. It occurs when the dominant allele is not able to mask the effect of the recessive allele completely. It is commonly seen in Snapdragon and Mirabilis jalapa. In F$ _2$ generation, the red allele cannot completely mask the effect of white allele resulting in a new phenotype i.e. pink.
Pink flowered progeny of red and white flowered parents of Antirrhinum majus is produced due to
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Dominance
-
Epistasis
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Codominance
-
Incomplete dominance
Incomplete dominance is the condition when none of the factors of a gene is dominant and the phenotype of a heterozygous dominant individual is a blend of dominant and recessive traits. For example, flower colour in Antirrhinum majus shows incomplete dominance and the monohybrid cross between two pure varieties gives 1 red : 2 pink : 1 white phenotypic ratio in F$ _2$ generation. Here, the heterozygous genotypes show the blending of dominant and recessive phenotypes. Epistasis is the non-allelic gene interaction where the presence of one gene masks the expression of another gene; it is an attribute of polygenic trait while flower colour in Antirrhinum majus is controlled by a single gene; option B is wrong. As we know that, a trait is represented by two contrasting factors of a gene in a heterozygous individual; the allele/factor that can express itself in a heterozygous individual is called as a dominant trait. The other factor whose effect is masked by the presence of dominant factor is called as the recessive factor. A cross between pure breeding dominant and recessive varieties produces all dominant varieties which are not the case in flower colour in Antirrhinum majus; option A is incorrect. When both recessive and dominant traits are expressed in a heterozygous genotype; it is codominance; but in Antirrhinum majus, a new blending trait is expressed in heterozygous genotype, option C is incorrect.
Incomplete dominance was discovered in
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Antirrhinum majus
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Mirabilis jalapa
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Pisum sativum
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Both A and B
Incomplete dominance is the condition when the dominant allele is not able to mask the effect of recessive allele completely. This results in an organism showing a physical appearance with a blend of both the alleles. It is also called partial dominance.
Allelic sequence variations where more than one variant (allele) at a locus in a human population is with a frequency greater than 0.01 is referred to as
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Incomplete dominance
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Multiple allelism
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SNP
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EST
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DNA polymorphism
Incomplete dominance means that one allele for a trait is not completely dominant over the other one and thus the heterozygous genotype shows a combination of dominant and recessive phenotypes. Mirabilis plant shows incomplete dominance of flower colour. Multiple allelism is a condition when more than two alleles of a gene govern the trait. Human blood group inheritance is the example of multiple alleles. It is governed by three alleles namely I$^{A}$, I$^{B}$ and I$^{A}$ and I$^{B}$ show codominance while allele i is recessive to both "I$^{A}$" and "I$^{B}$". This gives total six genotypes and four phenotypes- A (I$^{A}$ I$^{A}$ and I$^{A}$i), B (I$^{B}$ I$^{B}$ and I$^{B}$i), AB (I$^{A}$ I$^{B}$) and O (ii).
coding region of a gene and is used to identify the full-length genes in gene mapping. It is derived from cDNA, i.e., DNA formed using RNA template via reverse transcription.
DNA polymorphism can be defined as a condition where more than one different normal nucleotide sequences can exist at the same locus in DNA. These two different alleles are the product of single base pair mutation, deletions, insertions etc.
Incomplete dominance was first discovered by
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Mendel
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Hugo de Vries
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Carl Correns
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Tschermak
- Gregor Mendel was the founder of modern genetics. He performed experiments of on pea plant and established many rules of heredity, now referred to as the laws of Mendelian inheritance.
- Hugo de Vries gave the concept of genes, rediscovered laws of heredity, introduced the term mutation and gave the mutation theory of evolution.
- Carl Correns is known for his independent discovery of the principles of heredity and also discovered non-mendelian inheritance like cytoplasmic inheritance or cytoplasmic inheritance.
- Tschermark developed several new disease-resistant crops. Along with Vries and Correns, he discovered Gregor's work.
Mendel's experiments could not explain
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Incomplete dominance
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Segregation
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Recessiveness
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Dominance
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Independent assortment
Mirabilis jalapa shows
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Codominance
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Incomplete dominance
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Dominance
-
Complementary genes
Incomplete dominance is the condition when none of the factors of a gene is dominant; the phenotype of a heterozygous dominant individual is a blend of dominant and recessive traits. A monohybrid cross between two pure varieties of Mirabilis jalapa with red (RR) and white (rr) flowers gives red, pink and white colored flowers in 1:2:1 phenotypic ratio in $F _2$ generation. This is because the red color exhibits incomplete dominance over white color and the heterozygous dominant genotype (Rr) produces different phenotype from homozygous dominant (RR). Flower color in Mirabilis jalapa is governed by a single gene. Thus, the correct answer is option B.
A red snapdragon flower is crossed with a white snapdragon flower, and all the resulting flowers from the cross are pink. Which type of inheritance is occurring here?
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Incomplete dominance
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Codominance
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Sex-linked inheritance
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Pleiotropy
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Polygenic inheritance
Incomplete dominance is also called
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Intermediate inheritance
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Blending inheritance
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Partial dominance
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All the above
Mendel did not propose
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Dominance
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Incomplete dominance
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Segregation
-
Independent assortment
A.Law of dominance – When two contrasting alleles for a character come together in an organism, only one is expressed and another one is not expressed. Expressed character is called Dominant character and the character which is not expressed is called Recessive character
B.Incomplete dominance – Expression of new phenotypes in the progeny, other than the parents is called Incomplete dominance
C.Segregation – This law states both parental alleles of F1 generation separate and are expressed phenotypically in F2 generation
D.Independent assortment – When a cross is made between two individuals different from each other in two or more characters, then the inheritance of one character is independence of the inheritance of another character
So, the correct answer is ‘Incomplete dominance’
Phenotypic and genotypic ratio in $F _2$ generation in incomplete dominance is
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1 : 2 : 1 and 1 : 2 : 1
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3 : 1 and 1 : 2 : 1
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9 : 6 and 3 : 1
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9 : 3 : 3 : 1 and 1 : 2 : 1 : 4 : 1 : 1 : 2 : 1 : 2 : 1.
Appearance of new phenotypes or intermediate phenotypes, other than parental phenotypes in progeny is incomplete dominance. In this, In the F2 generation, 1 red flowered plants(RR), two pink flowered plants(Rr), 1 white flowered plants(rr) are formed. So, the phenotypic and genotypic ratio is 1:2:1.
So, the correct option is ‘1:2:1 and 1:2:1’.
A plant having 24 cm long internodes is crossed with a plant having 12 cm long internodes. The hybrids have 18 cm long internodes due to
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Multiple allelism
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Complete dominance
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Recessive dominance
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Incomplete dominance
Appearance of new phenotypes or intermediate phenotypes, other than parental phenotypes in progeny is incomplete dominance. A plant having 24cm long internodes is crossed with plant having 12cm long internodes. In the hybrids 18cm long internodes appear. It is due to blending of characters. So, it is called Incomplete dominance or blending inheritance.
So, the correct option is ‘Incomplete dominance’.
Which one is exception to Mendel's principle of dominance?
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Wild Pea
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Mirabilis
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Garden Pea
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Maize
Gregor Johann Mendel, an Austrian Monk, discovered the principles of heredity through the experiments on the pea plant. Mendel conducted hybridization experiments on garden peas for seven years and proposed the laws of inheritance in living organisms. They are Law of dominance, Law of segregation, Law of Independent assortment. These laws are exceptional in some cases like incomplete dominance, co-dominance, etc.
So, the correct option is ‘Mirabilis’.
$F 2$ generation has genotypic and phenotypic ratio 1 : 2 : 1. It is _______________.
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Codominance
-
Dihybrid cross
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Monohybrid cross with complete dominance
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Monohybrid cross with incomplete dominance.
A.Codominance – Phenotypic and genotypic ratio is 1:2:1
B.Dihybrid cross – Phenotypic ratio is 9:3:3:1 and genotypic ratio is 1:2:2:4:1:2:1:2:1
C.Monohybrid cross with complete dominance – phenotypic ratio is 3:1 and genotypic ratio is 1:2:1
D.Monohybrid cross with incomplete dominance - Phenotypic and genotypic ratio is 1:2:1
So, the correct option is ‘Codominance & Monohybrid cross with incomplete dominance’.
In Antirrhinum (dog flower), phenotypic ratio in $F _2$ generation for the inheritance of flower colour would be
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3:1
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1:2:1
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1:1
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2:1
The inheritance of flower colour in the Antirrhinum majus (snapdragon or dog flower) is an example of incomplete or partial dominance. Incompleted dominance is the phenomenon in which neither of the two alleles of a gene is completely dominant over the other. In a cross between true-breeding red-flowered (RR) and true-breeding white-flowered plants (rr), the $F _1$ plants obtained were pink (Rr) coloured. When the $F _1$ plants were self-pollinated, the $F _2$ generation resulted in the ratio, 1 (RR) Red :2 (Rr) Pink: 1 (rr) White. The phenotypic ratios had changed from the normal 3 : 1 dominant : recessive ratio to 1: 2: 1. R was not completely dominant over rand this made it possible to distinguish Rr (pink) from RR (red) and rr (white).
So, the correct answer is '1:2:1'.
Phenotypic and genotypic ratio is similar in case of ________________.
-
Complete dominance
-
Incomplete dominance
-
Over dominance
-
Epistasis
Incomplete dominance is the phenomenon of neither of the two alleles being dominant so that expression in the hybrid is intermediate between the expressions of the two alleles in homozygous state. $F _2$ phenotypic ratio is : 2 : 1, similar to genotypic ratio.
Please select the structural character of community.
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Dominance
-
Physiognomy
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Decomposition
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$1$ and $2$ both
The phenotype ratio of a dihybrid cross in which both the genes show incomplete dominance is
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1 : 2 : 1
-
9 : 3 : 3 : 1
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1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1
-
3 : 1
- Incomplete dominance is the condition where a dominant trait fails to show dominance completely in the heterozygous condition. For example, in snapdragon homozygous dominant results in the red color of the flower while homozygous recessive results in white flower. While heterozygous condition results in the pink color of the flower.
- Hence, in each case of incomplete domination, the heterozygous condition will result in a new phenotype.
- Following Punnet's square is representing dihybrid cross for genes A and B showing incomplete domination - | | AB | Ab | aB | ab | | --- | --- | --- | --- | --- | | AB | AABB | AABb | AaBB | AaBb | | Ab | AABb | AAbb | AaBb | Aabb | | aB | AaBB | AaBb | aaBB | aaBb | | ab | AaBb | Aabb | aaBb | aabb |
- As we can see by counting phenotype ratio is same as genotype ratio here i.e. 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1.
- So, the correct option is '1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1'.
The number of classes of phenotypes in the $F 2$ of a cross between dihybrids involving both the genes with incomplete dominance would be_____
-
Six
-
Nine
-
Sixteen
-
Eight
Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles. In this case, the F2 generation of a cross between dihybrids involving both the genes with incomplete dominance would result in developing eight different classes of phenotypes as evident from the calculation and phenotype variation in the Punnett square.
A heterozygous round seeded pea plant is crossed with wrinkled seeded pea plant. How many plants produces intermediate sized starch grain out of 2000 progenies obtained?
-
1000
-
0
-
1500
-
750
- The starch synthesis in pea plants is controlled by a single gene which has two alleles B and b.
- BB (homozygote) seeds were round whereas, bb was wrinkled.
- The ratio obtained is 1 (long grain): 2 (intermediate grain): 1 (small grain), therefore, out of 2000 progenies obtained 1000 progenies have intermediate size starch grain.
Both phenotypic and genotypic ratio of $F _2$ are same in
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Co-dominance
-
Incomplete dominance
-
Back cross
-
Both A and B
Exception to Mendel's law is found in flower colour of
-
$Mirabilis$
-
Sweet pea
-
Garden pea
-
Beans
Exception to Mendel's laws can be explained in Mirabilis jalapa with incomplete dominance. Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes. Incomplete genetic dominance is similar to, but different from co-dominance. In co-dominance, an additional phenotype is produced, however both alleles are expressed completely. Co-dominance is exemplified in AB blood type inheritance. Example: Incomplete dominance is seen in cross-pollination experiments between red and white snapdragon plants. The allele that produces the red color (R) is not completely expressed over the recessive allele that produces the white color (r). The resulting offspring are pink. The genotypes are: (RR) Red, (rr) White, and (Rr) Pink.
When phenotypic and genotypic ratio is the same, then it is an example of ___________
-
Incomplete dominance
-
Cytoplasmic inheritance
-
Quantitative inheritane
-
Incomplete or co-dominance
In case of incomplete dominance, F$ _2$ generation has
-
Genotypic ratio equal to phenotypic ratio
-
Genotypic ratio is 3:1
-
Phenotypic ratio is 3:1
-
None of the above
Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes.
Incomplete genetic dominance is similar to, but different from co-dominance. In co-dominance, an additional phenotype is produced, however both alleles are expressed completely. Co-dominance is observed in AB blood type inheritance.
Example: Incomplete dominance is seen in cross-pollination experiments between red and white snapdragon plants. The allele that produces the red color (R) is not completely expressed over the recessive allele that produces the white color (r). The resulting offspring are pink. The genotypes are: (RR) Red, (rr) White, and (Rr) Pink.
In case of incomplete dominance, F$ _{2}$ generation has genotypic ratio equal to phenotypic ratio.
Plant, which does not obey Mendel's laws is
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Mirabilis jalapa
-
Pisum sativum
-
Iberis amara
-
None of the above
It is a type of intragenic (or interallellic) interaction, where both the alleles of a given trait express as a blend (mixture) as against a normal Mendelian pattern, where one allele is dominant over the other. As a resulting of this blending, an intermediate character is expressed. This situation occurs due to the fact that the dominant gene is not in a position to completely suppress the expression of recessive gene. With the result, the heterozygous offspring will be phenotypically and genotypically different from either of the homozygous parent. Following are the two familiar examples of incomplete dominance.
Incomplete dominance occurs in
-
$Mirabilis$
-
$Antirrhinum$
-
Andulasion fowl
-
All of the above
Pink roses are often the result of incomplete dominance. When red roses, which contain the dominant red allele, are mated with white roses (which is recessive), the offspring will be heterozygotes, and will express a pink phenotype.
Examples are:
A snapdragon flower that is pink as a result of cross-pollination between a red flower and a white flower when neither the white or the red alleles are dominant.
A brown fur coat on a rabbit as a result of one rabbit's red allele and one rabbit's white allele not dominating.
A child with wavy hair as a result of one parent's curly hair and the other's straight hair.
An Andalusian fowl produced from a black and a white parent is blue.
A carnation that is pink that is a result of cross-pollination between a red carnation and a white carnation.
A black sheep and a white sheep mate and have a grey sheep.
A black dog and a brown dog mate and the result is a dog with a brindle coat.
A white cat and a brown cat mate and the result is an orange cat.
A tall horse and short horse mate and the offspring is off medium stature.
A big American bulldog and a small American bulldog mate and their offspring is medium-sized.
A long tailed dog and a short tailed dog mate and the offspring has a medium lengthened tail.
A blue bird and a red bird mate and the resulting offspring have mixed colors.
Incomplete dominance is found in
-
Pisum sativum
-
Antirrhinum majus
-
Both Pisum sativum and Antirrhinum majus
-
None of the above
Incomplete dominance is a form of intermediate inheritance, in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes.
Incomplete genetic dominance is similar to, but different from co-dominance. In co-dominance, an additional phenotype is produced, however, both alleles are expressed completely.
Co-dominance is exemplified in AB blood type inheritance.
Example: Incomplete dominance is seen in cross-pollination experiments between red and white snapdragon plants. The allele that produces the red color (R) is not completely expressed over the recessive allele that produces the white color (r). The resulting offspring are pink. The genotypes are: (RR) Red, (rr) White, and (Rr) Pink.
In Mirabilis jalapa, if the $F _1$ pink flowered plants are crossed with white-flowered plants, the progeny will be
-
All pink flowered plants
-
1 pink : 2 red : 1 white
-
1 pink : 1 white
-
3 red : 1 white
R | r | |
---|---|---|
r | Rr (pink) | rr (white) |
r | Rr (pink) | rr (white) |
Crossing between F$ _1$ generation and the recessive parent is called a test cross.
Which of the following is a deviation from Mendelian principle ?
-
Inheritance of AB blood groups in man
-
Inheritance of flower colour in Mirabilis jalapa
-
Inheritance of cotyledon colour in Pisum sativum
-
Inheritance of AB blood group in man and flower colour in Mirabilis jalapa
Co-dominance | A | B |
---|---|---|
A | AA | AB |
B | AB | BB |
Incompletedominance | R | r |
---|---|---|
R | RR | Rr |
r | Rr | rr |
Inheritance of AB blood group in human follows co-dominance while inheritance of flower colour in Mirabilis jalapa follows incomplete dominance.
-
Females prefer the brighter plumage and so mate with this phenotype more often.
-
The dull plumage provides a selection advantage over the bright plumage.
-
The adults with dull plumage require less energy investment to ensure their survival.
-
Those brightly colored birds that do survive have more highly developed survival skills than those that do not survive.
-
Dull-colored adult males are more lethargic than the brightly colored birds.
Dull plumage confers a survival advantage to birds by protecting them against predators while those having brighter plumage are easily spotted. However, brighter plumage helps male birds to attract female birds for mating and confers reproductive advantage. This leads to persistence of brighter plumage population despite its more chances to get captured by a predator. Thus, the correct answer is option A.
A pea plant with round seeds having large starch grains is crossed with another pure pea plant with wrinkled seeds having small starch grains. The $F _1$ heterozygotes formed are self pollinated. What is the phenotypic ratio of plants with round seeds and intermediate starch grains to plants with wrinkled seeds and larger starch grains expected in $F _2$ generation
-
5 : 6
-
2 : 3
-
3 : 4
-
6 : 1
A pea plant with round seeds having large starch grains is crossed with another pea plant with wrinkled seeds having small starch grains. The F1 heterozygotes formed self-pollinated. The phenotypic ratio of plants with round seeds and intermediate starch grains to plants with wrinkled seeds and larger starch grains in F2 generation are 6:1.
So, the correct option is ‘6:1’
The inheritance of flower color in Antirrhinum (dog flower) is an example of
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incomplete dominance
-
co-dominance
-
multiple alleles
-
linkage
In the dog flower Antirrhinum there are two types of flower color in pure state: red and white. When the two types of plants are crossed, the hybrid or plants of generation have pink flowers. This is due to a phenomenon called the incomplete dominance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles ( in this case the red and white color and incompletely dominant and hence the third color pink is observed when they mix).
What percentage of progenies would have broad leaves and pink flower in F2 generation of Snapdragon if the first trait follows the law of dominance and the other shows incomplete dominance?
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37.5%
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56.25%
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62.5%
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12.5%
Assume that the broad shape of leaves is governed by alleles B,b where 'B' represents dominant allele for broad leaves. Similarly, 'R' and 'r' are alleles for the colour of the flower. 'RR' progenies show red colour,' rr' progenies show white colour and 'Rr' progenies show pink colour due to incomplete domination.
Gamete type | BR | Br | bR | br |
---|---|---|---|---|
BR | BBRR | BBRr | BbRR | BbRr |
Br | BBRr | BBrr | BbRr | Bbrr |
bR | BbRR | BbRr | bbRR | bbRr |
br | BbRr | Bbrr | bbRr | bbrr |