Genetics Question: Artificial selection for fruit weight is carried out in a tom

Question

Genetics Question:

Artificial selection for fruit weight is carried out in a tomato population. From each plant, all the fruits are weighed, and the average weight per tomato is regarded as the phenotype of the plant. In the population as a whole, the average fruit weight per plant is 75 grams. Plants whose fruitweight averages 100 grams per tomato are selected and mated at random to produce the next generation. The narrow-sense heritability of average fruit weigh in this population is estimated to be 20 percent.

A. What is the expected average fruit weight among plants after one generation of selection?

B. What is the expected average fruit weight among plants after five consecutive generationsof selection, when, in each generation, the chosen parents have an average fruit weight 25 grams above the population average in that generation? Assume that the narrow sense heritability remains constant during this time.

Explanation / Answer

1. The mean of the population is 75gms and weight of the selected plant is 100gms.

Narrow sense heritability is 0.20

Average fruit weight after one generation is given by

75+ (0.20)(100-75)= 80 grams per tomato

2. The average fruit weight after 5 generation is 25 grams

Narrow sense heritability is 0.20

Then the expected gain per generation is 5 grams, after 5 generations the expected weight is 25 grams.

Then the expected average fruit weight among plants after 5 consecutive generations would be 75+25= 100 grams

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