Question

1)An inbred strain of rice has a mean yield of 8 g dried rice per plant. A second inbred strain has a mean yield of 32 g. Crossing the two strains produces an F1 that has a mean yield of 20 g. The F2 have a continuous range of yields with most plants around 20 g rice/plant. 4 out of 800 plants are at 8 g rice/plant, and 4 out of 800 at 32 g rice/plant. How many genes contribute to yield variation in rice?

2)Referring to the above problem, how much does each additive allele contribute to yield?

For full credit show your calculations,

Answer 1

• In polygenic inheritance or quantitative inheritance more than one genes control the same trait to give additive effect in determining the phenotype.
• That is quantitative traits are governed by multiple genes present at different gene loci with each gene contributing the same amount to the phenotype
• Large number of phenotypic intermediates with two extreme phenotypes which are identical to the parental type are obtained in progenies.
• No. Of genes contributing to variance in weight of rice plant = 4
• Contribution of each allele in weight or rice plants(yield) = 3 grams
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