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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:
Homozygous and Heterozygous
How would you find out whether a given tall garden pea plant is homozygous or heterzygous? Substantiate your answer with the help fo Punnett squares.
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.
Explain Mendel’s monohybrid progeny with the help of any one cross.
Name the conditions when both the alleles are identical?
A garden pea plant produces axial white flowers. Another of the same species produced terminal violet flowers. Identify the dominant trait?
A pure tall plant (TT) is crossed with the pure dwarf plant (tt), what would be the F1 and F2 generations? Explain.
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.
What do the plants of the F1 generation look like?
Genotypic ratio of a monohybrid cross is ______.
Cross between hybrid and recessive parent:
Assertion (A): In humans, if gene (B) is responsible for black eyes and gene (b) responsible for brown eyes, then the colour of eyes of the progeny having gene combination Bb, bb or BB will be black only.
Reason (R): The black colour of the eyes is a dominant trait.
A monohybrid cross is a genetic cross in which how many pair(s) of contrasting characters is/are studied?
Which pair of contrasting characters is studied in the pea plant monohybrid cross?
Mendel used a monohybrid cross to understand how which feature passes from parents to offspring?
What are the phenotype and genotype of all offspring produced by \[TT \times tt\]?
Which conclusion follows from the tall and dwarf pea plant monohybrid cross?
