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Ch. 25 - Quantitative Genetics and Multifactorial Traits
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 25 - Quantitative Genetics and Multifactorial TraitsProblem 28b
Chapter 25, Problem 28b

Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in modified form and content.
Table showing yearly flower diameter means in millimeters for control, selected parents, and offspring from 1997 to 1999.
Calculate the realized heritability for each year and the overall realized heritability. 

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1
Step 1: Understand the concept of realized heritability. Realized heritability (h^2) is calculated using the formula: h^2 = R / S, where R is the response to selection (difference between offspring mean and control mean) and S is the selection differential (difference between selected parents mean and control mean).
Step 2: For each year, calculate the selection differential (S). Use the formula S = Mean of selected parents - Mean of control. For example, for 1997, S = 34.13 - 30.04.
Step 3: For each year, calculate the response to selection (R). Use the formula R = Mean of offspring - Mean of control. For example, for 1997, R = 32.21 - 30.04.
Step 4: Calculate the realized heritability (h^2) for each year using the formula h^2 = R / S. Perform this calculation for 1997, 1998, and 1999 using the values of R and S obtained in the previous steps.
Step 5: To find the overall realized heritability, average the h^2 values calculated for each year. This provides a single value representing the overall heritability across all years.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Realized Heritability

Realized heritability is a measure of the proportion of phenotypic variance in a trait that can be attributed to genetic variance, as observed in a specific population under certain environmental conditions. It is calculated using selection experiments, where the response to selection is compared to the initial phenotypic variance. This concept is crucial for understanding how traits can evolve over generations through natural or artificial selection.
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Artificial Selection

Artificial selection is a process in which humans intentionally breed plants or animals for specific traits, such as flower size in Phlox drummondii. This method allows researchers to observe the effects of selective pressure on trait variation and can provide insights into the genetic basis of those traits. By manipulating breeding, scientists can study how traits are inherited and how quickly they can change in a population.
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Phenotypic Variation

Phenotypic variation refers to the observable differences in traits among individuals in a population, which can be influenced by both genetic and environmental factors. In the context of the question, flower size is a trait that exhibits phenotypic variation, and understanding this variation is essential for calculating realized heritability. It highlights the importance of measuring traits accurately to assess their genetic basis and evolutionary potential.
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Related Practice
Textbook Question

Consider a true-breeding plant, AABBCC, crossed with another true-breeding plant, aabbcc, whose resulting offspring are AaBbCc. If you cross the F₁ generation, and independent assortment is operational, the expected fraction of offspring in each phenotypic class is given by the expression N!/M!(N−M)! where N is the total number of alleles (six in this example) and M is the number of uppercase alleles. In a cross of AaBbCc×AaBbCc, what proportion of the offspring would be expected to contain two uppercase alleles?

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Textbook Question

Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in a modified form and content.

Considering that differences in control values represent year-to-year differences in greenhouse conditions, calculate (in mm) the average response to selection over the three-year period

421
views
Textbook Question

Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in modified form and content.

Considering that differences in control values represent year-to-year differences in greenhouse conditions, calculate (in mm) the average response to selection over the three-year period. 

429
views
Textbook Question

Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in modified form and content.

Assuming that the realized heritability in phlox is relatively high, what factors might account for such a high response?

418
views
Textbook Question

Floral traits in plants often play key roles in diversification, in that slight modifications of those traits, if genetically determined, may quickly lead to reproductive restrictions and evolution. Insight into genetic involvement in flower formation is often acquired through selection experiments that expose realized heritability. Lendvai and Levin (2003) conducted a series of artificial selection experiments on flower size (diameter) in Phlox drummondii. Data from their selection experiments are presented in the following table in modified form and content.

In terms of evolutionary potential, is a population with high heritability likely to be favored compared to one with a low realized heritability? 

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Textbook Question

In 1988, Horst Wilkens investigated blind cavefish, comparing them with members of a sibling species with normal vision that are found in a lake [Wilkens, H. (1988). Evol. Biol. 25:271–367]. We will call them cavefish and lakefish. Wilkens found that cavefish eyes are about seven times smaller than lakefish eyes. F₁ hybrids have eyes of intermediate size. These data, as well as the F₁ × F₁ cross and those from backcrosses (F₁ × cavefish and F₁ × lakefish), are depicted below. Examine Wilkens's results and respond to the following questions:

Based strictly on the F₁ and F₂ results of Wilkens's initial crosses, what possible explanation concerning the inheritance of eye size seems most feasible? 

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