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प्रश्न
Describe the dihybrid cross upto F2 generation as conducted by Gregor Mendel using pure lines of Garden Pea for characters-seed shape and seed colour.
उत्तर
Yellow colour was dominant over green and round shape was dominant over wrinkled. These results were identical to those that he got when he made separate monohybrid crosses between yellow and green-seeded plants and between round and wrinkled-seeded plants. Let us use the genotypic symbols Y for the dominant yellow seed colour and y for the recessive green seed colour, R for round-shaped seeds and r for wrinkled seed shape. The genotype of the parents can then be written as RRYY and rryy. The cross between the two plants can be written down showing the genotypes of the parent plants. The gametes RY and ry unite on fertilisation to produce the F1 hybrid RrYy. When Mendel self-hybridised the F1 plants, he found that 3/4th of F2 plants had yellow seeds and 1/4th had green. The yellow and green colours are segregated in a 3 : 1 ratio. Round and wrinkled seed shapes are also segregated in a 3 : 1 ratio; just like in a monohybrid cross. In the dihybrid cross Figure, the phenotypes round, yellow; wrinkled, yellow; round, green and wrinkled, green appeared in the ratio 9 : 3 : 3 : 1. Such a ratio was observed for several pairs of characters that Mendel studied. The ratio of 9 : 3 : 3 : 1 can be derived as a combination series of 3 yellow : 1 green, with 3 round : 1 wrinkled. This derivation can be written as follows: (3 Round : 1 Wrinkled) (3 Yellow : 1 Green) = 9 Round, Yellow : 3 Wrinkled, Yellow: 3 Round, Green : 1 Wrinkled, Green Based upon such observations on dihybrid crosses (crosses between plants differing in two traits) Mendel proposed a second set of generalisations that we call Mendel’s Law of Independent Assortment. The law states that ‘when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters’.
Phenotypic ratio:
| round yellow : round green : wrinkled yellow : wrinkled green |
| 9 3 3 1 |
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संबंधित प्रश्न
Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in F1 generation for a dihybrid cross?
Filling the blank based on the given relationship.
3 : 1 Monohybrid : : 9 : 3 : 3 : 1 : ______
What is a dihybrid cross? How did Mendel perform this cross?
Give Technical Term:
The ratio of offspring on F2 generation in a dihybrid cross.
Complete the following sentence with appropriate word:
_______ is the ratio of dihybrid cross.
Complete the following sentence with appropriate word:
A character that is suppressed is _________.
The physical expression of a gene is called ______.
Select the period for Mendel’s hybridization experiments
Among the following characters which one was not considered by Mendel in his experimentation pea?
Identify the statementls that is/are NOT the correct reason/s for Mendel's success in his hybridization experiments.
i. Each factor controlled the single trait and is located on separate chromosomes.
ii. In the pea plant, contrasting characters can be easily recognized.
iii. Mendel carefully recorded the number of plants of each type and expressed his results as ratios.
iv. Mendel performed biochemical assays for identifying the position of 'factors' on chromosome.
Two linked genes a and b show 20% recombination. The individuals of a dihybrid cross between ++ /++ × ab/ab shall show gametes ______.
In a dihybrid cross, F2 phenotypic ratio is 13 : 3. It is case of ______.
Mendel’s Law of independent assortment holds good for genes situated on the ______.
Each gamete carry ______.
Two pea plants - one with round yellow seeds (RRYY) and another with wrinkled green (rryy) seeds produce F1 progeny that have round, yellow (RrYy) seeds.
When F1 plants are self-pollinated, which new combination of characters is expected in F2 progeny? How many seeds with these new combinations of characters will be produced when a total 160 seeds are produced in F2 generation? Explain with reason.
Sahil performed an experiment to study the inheritance pattern of genes. He crossed tall pea plants (TT) with short pea plants (tt) and obtained all tall plants in F1 generation.
When F1 plants were self-pollinated, a total of 800 plants were produced. How many of these would be tall, medium height or short plants? Give the genotype of F2 generation.
The Law of independent assortment is applicable for the traits which ______
