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प्रश्न
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?
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उत्तर
The following Punnett Square shows a cross between a tall plant with red flowers (TTRR)and a dwarf plant with white flowers (ttrr). All the plants in F1 generation will be tall and will produce red flowers.
When plants of F1 generation are allowed to self-pollinated, phenotype of plants in F2 generation can be shown by following Punnett Square.
In this case, the standard dihybrid ratio 9 : 3 : 3 : 1 which can be shown as follows:
Tall plant red flower = 9
Tall plant white flower = 3
Dwarf plant red flower = 3
Dwarf plant white flower = 1
The standard dihybrid ratio works only when the genes for contrasting characters are on different chromosomes. If characters are on the same chromosome, they may interact with each other. In that situation, the dihybrid ratio would show variation from the standard hybrid ratio.
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संबंधित प्रश्न
Differentiate between the following:
Dominance and Recessive
Differentiate between the following:
Monohybrid and Dihybrid
Explain Mendel’s monohybrid progeny with the help of any one cross.
Mention whether the cross is a monohybrid or dihybrid.
Answer the following question.
Write the basis on which Alfred Sturtevant explained gene mapping.
What is a monohybrid cross? How did Mendel perform this cross?
A certain couple got four daughters in a sequence and no son. Does it mean that the husband does not produce Y-chromosome bearing sperms? Explain. What is the chance of this couple having a daughter?
Name the conditions when both the alleles are identical?
Pure-bred tall pea plants are first crossed with pure-bred dwarf pea plants. The pea plants obtained in the F1 generation are then selfed to produce F2 generation of pea plants.
Which type of plants was missing in the F1 generation but reappeared in the F2 generation?
Differentiate between inherited and acquired characters. Give one example for each type.
Give reasons why acquired characters are not inherited.
Genotypic ratio of a monohybrid cross is ______.
When a tall plant with rounded seeds (TTRR) is grossed with a Dwarf plant with wrinkled seeds (ttrr) the F1 generation consists of tall plants with rounded seeds. How many types of gametes the F1 plant would produce?
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 cross between red coloured and white coloured flowers, when plants with red coloured flowers of F1 generation were self pollinated, plants of F2 generation were obtained in which 75% of plants were with red flowers and 2.5% plants were with white flowers.
Explain the inheritance of traits in the above cross with the help of a flow chart only along with the ratio of plants obtained.
