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प्रश्न
Given below are the F2 – phenotypic ratios of two independently carried monohybrid crosses :
(i) 1 : 2 : 1
(ii) 3 : 1
Mention what does each ratio suggest.
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उत्तर
(i) 1 : 2 : 1 - Phenotypic ratio
Suggest that the phenomenon is incomplete dominance
* When neither of the alleles of a character is completely dominant over the other and the F1 hybrid is intermediate between the two parents, the phenomenon is Incomplete dominance.
* The phenotypic and genotypic ratio in F2 generation is 1:2:1 in this case.
(ii) 3:1 - Phenotypic ratio
Suggest that the phenomena has monohybrid cross. Monohybrid cross is a cross which involves only a single pair of contrasting characters. The parental generation has genotype for pure gene which on cross produces homozygous progeny i.e. F1 generation. On selfing F1 generation obtain F2 generation. The F2 generation has phenotypic ratio 3 : 1.
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संबंधित प्रश्न
Differentiate between the following:
Monohybrid and Dihybrid
Explain Mendel’s monohybrid progeny with the help of any one cross.
Differentiate Between Monohybrid and Dihybrid cross.
What do you understand by the terms phenotype and genotype?
A Monohybrid cross is ______
Cross between hybrid and recessive parent:
In a monohybrid cross of plants with red and white flowered plants, Mendel got only red-flowered plants. On self-pollinating these F1 plants got both red and white flowered plants in 3:1 ratio. Explain the basis of using RR and rr symbols to represent the genotype of plants of parental generation.
In a plant tallness is dominant over dwarfness and red flower is dominant over white. Starting with the parents work out a dihybrid cross. What is standard dihybrid ratio? Do you think the values would deviate if the two genes in question are interacting with each other?
Pooja has green eyes while her parents and brother have black eyes. Pooja’s husband Ravi has black eyes while his mother has green eyes and father has black eyes.
a. On the basis of the above given information, is the green eye colour a dominant or recessive trait? Justify your answer
b. What is the possible genetic makeup of Pooja’s brother’s eye colour?
c. What is the probability that the offspring of Pooja and Ravi will have green eyes? Also, show the inheritance of eye colour in the offspring with the help of a suitable cross.
OR
c. 50% of the offspring of Pooja’s brother are green eyed. With help of cross show how this is possible.
Given below is a schematic representation of the inheritance of the shape of the seeds of garden peas. Answer the questions that follow:
- Which is the dominant and recessive allele of the trait?
- What does the ratio 3 : 1 in the F2 generation represent?
- State Mendel's Law of Dominance.
