Question

78. In a particular plant, two genes control leaf shape and color. Round leaves (R) are dominant to
jagged leaves (). Yellow fruits (Y) are dominant to white fruits (y). A true-breeding round-
leaved, yellow-fruited plant is mated with a jagged-leaved, white-fruited plant. What are the
genotypes of the plants involved in this cross?
1) RRYY X RRYY 2) RRYY x rryy 3) RrYyx RrYy 4) RrYy x rryy​

Answer 1

Answer:  option 2 and 4

Explanation:

Answer 2

Option (2)is the correct answer B RRYY x rryy

Explanation:

• In a particular plant, two genes control leaf shape and color. Round leaves (R) are dominant to jagged leaves (). Yellow fruits (Y) are dominant to white fruits (y). A true-breeding round-leaved, yellow-fruited plant is mated with a jagged-leaved, white-fruited plant.
• A true-breeding plant is result of continuous self pollination which has stable inheritance and expression of certain traits for several generations. These are pure line breeds.

• True breeding plants are known as homozygous.

• Here the genotype will be identical alleles for a character.

• As given in the question the plant differs in two characteristics- the shape of the leaf and the color of the fruit. So it is an example of a dihybrid cross.
• According to the question, round leaves (R) are dominant to jagged leaves (r), and yellow fruits (Y) are dominant to white fruits (y).

• Therefore, pure round-leaved and yellow fruited plants would be represented as RRYY  which is homozygous and are dominant for both the genes and they are pure jagged-leaved and white fruited plants would be represented as rryy (recessive for both the genes).
• Thus, the genotypes of the parent plants involved in this cross are RRYY X rryy.

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