Question

In pea plants, yellow seeds are dominant to green. If a heterozygous yellow seeded plant is crossed with a green seeded plant, what ratio of yellow and green seeded plant would you expect in F1 generation?

A) 50:50

B) 9:1

C) 1:3

D) 3:1

Answer 1

Mendel conducted artificial pollination or cross-pollination experiments using several true-breeding pea lines A true breeding line is one that having undergone continuous self-pollination, shows the stable trait inheritance and expression for several generations.

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Complete Answer:

• Mendel selected a total of 14 true-breeding pea plant varieties, such as the height of the stem whether tall or dwarf, as pairs which were similar except for one character with contrasting traits. It means, Mendel selected 7 characters that are seed shape, seed colour, pod colour in pea plant for carrying out hybridisation experiments and to study inheritance
• When a heterozygous yellow seed is crossed with a green seeded plant it is an example of monohybrid cross.
• Study of inheritance of a single pair of contrasting traits of a character at a time is called one gene inheritance.
• Mendel crossed true breeding yellow seeds and true breeding green seeds from a variety of pea plants to study the inheritance of one gene.
• The plants used in the initial cross are referred to as P1 and P2 or parents. Since pea is self-fertilising, the anthers should be removed from the female parent before maturity for the purpose of cross pollination.
• The method of removal of anthers from bisexual flowers of female parent plant is called emasculation.
• The pollen, then at the dehiscence stage, is brought from the male parent and is dusted on the stigma of emasculated flowers.
• He collected the seeds produced as a result of this cross and grew them to generate plants of the first hybrid generation. This generation is also called the filial, (offspring) progeny or the F1 generation.
• When Mendel self-pollinated the yellow seeded F1 plants, both yellow and green seeded plants were obtained in F2, generation.
• Offspring derived from the selfing of the F1, are termed as second filial or F2, generation. When a heterozygous yellow seed plant (Yy) is crossed with a green seed plant (yy), the progeny we obtained is two heterozygous yellow seeded plants (Yy) and two green seeded plants (yy). It means the ratio of yellow seed plant: green seeded plants is 50:50 or we can say that 1:1.

Therefore, the correct answer is option (A) that is 50:50.
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Note:** Mendel crossed pea plants differing in two characters (dihybrid cross) to verify the results of monohybrid crosses. This gave him a chance to understand inheritance of two pairs of factors like seed colour and shape at a time. A cross was made that allowed for pollination between a pure round yellow-seeded pea plant (RRYY) with wrinkled green-seeded pea plant (rryy). Yellow colour is dominant over green and round seed shape over wrinkled seed shape.