In a line of cherry tomatoes, the average fruit weight is 16 g. A plant producing tomatoes with an average weight of 12 g is used in one self-fertilization cross to produce a line of smaller tomatoes, and a plant producing tomatoes of 24 g is used in a second cross to produce larger tomatoes. What is the selection differential (S) for fruit weight in each cross?

Verified step by step guidance

1. Understand the concept of selection differential (S): It is the difference between the mean phenotype of the selected parents and the mean phenotype of the original population. In this case, it measures how much the average fruit weight of the selected parents deviates from the average fruit weight of the original population.
2. Identify the average fruit weight of the original population, which is given as 16 g.
3. For the first cross (smaller tomatoes): Determine the average fruit weight of the selected parent, which is 12 g. Calculate the selection differential (S) using the formula: $S=W$_selected-W_original, where $W$_selected is the average weight of the selected parent and $W$_original is the average weight of the original population.
4. For the second cross (larger tomatoes): Determine the average fruit weight of the selected parent, which is 24 g. Use the same formula to calculate the selection differential (S): $S=W$_selected-W_original.
5. Interpret the results: The selection differential (S) will indicate how much the selected parents deviate from the original population in terms of fruit weight. This value is important for understanding the strength of selection in each cross.

Key Concepts

Selection Differential (S)

The selection differential (S) is a measure of the difference between the mean phenotype of the selected individuals and the mean phenotype of the entire population. It quantifies the extent to which selected individuals differ from the average, indicating the strength of selection applied. In this context, S can be calculated by subtracting the average fruit weight of the selected plants (12 g or 24 g) from the average fruit weight of the original population (16 g).

Phenotypic Variation

Phenotypic variation refers to the observable differences in traits among individuals in a population, which can be influenced by genetic and environmental factors. Understanding phenotypic variation is crucial for predicting how traits like fruit weight can change over generations due to selection. In this scenario, the variation in fruit weight among the selected plants and the original population is essential for calculating the selection differential.

Self-Fertilization in Plants

Self-fertilization is a reproductive strategy where a plant fertilizes its own ovules with its own pollen, leading to offspring that are genetically similar to the parent. This method can stabilize certain traits within a population, making it useful for producing lines with specific characteristics, such as smaller or larger tomatoes in this case. Understanding self-fertilization helps in predicting the inheritance patterns of selected traits in subsequent generations.