Question

Q3 After self-pollination in pea plants with Tall height, yellow seeds, following types of seeds were obtained by Mendel:
Seeds. Number
Short, green. 65
tall green. 226
Tall, yellow 620
short, yellow. 201
Analyze the result and describe the mechanism of inheritance which explains these results.
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Answer 1

Answer:

In peas Tall (T) seeds are dominant over short (t) seeds and yellow (Y) seeds are dominant over green (y) seeds. When a cross is made between tall, yellow seeded (TTYY or TTYy or TtYY or TtYy) plant is crossed with short, green seeded (ttyy) plant, the number of progeny are 203 tall, green-seeded (TTyy or Ttyy) plants, 199 short, green-seeded (ttyy) plants, 207 tall, yellow-seeded (TTYY or TTYy or TtYY or TtYy) plants and 192 short, yellow seeded (ttYY or ttYy) plants.

Since, all four types of progeny are in the ratio of 1:1:1:1, this is an example of test cross. Test crosses is done to test the genotype of dominant parent (homozygous or heterozygous) by crossing it with a homozygous recessive parent. Hence, in the given example, the dominant parent is heterozygous and its genotype TtYy.

Thus, the correct answer is 'TtYy.