12th Class Biology Sample Paper Biology - Sample Paper-7

  • question_answer
    When a cross is made between tall plant yellow seeds (TtYy) and tall plant with green seed (Ttyy), what proportion of Phenol type in the offspring could be expected to be:
    (i)   tall and green         (ii) dwarf and green
    In peas, tallness is dominant over dwarfiiess, and red colour flowers is dominant over the white colour. When a tall plant bearing red flowers was pollinated by a dwarf plant bearing white flowers, the different phenotypic groups were obtained in the progeny in numbers, mentioned against them.
    (i) Tall, Red = 138         
    (ii) Tall, White = 132
    (iii) Dwarf, Rdd = 136
    (iv) Dwarf, White = 128


    The result shows that the four types of offsprings are in a ratio of 1 : 1 :1 :1. Such a result is observed in test-cross progeny of a dihybrid cross.
    The cross can be represented as:
    Tall and red (Tt Rr) \[\times \] Dwarf and White (ttrr)
    Genotype of two patrents - TtRr, ttrr.

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