Textbook Question
The following variances were calculated for two traits in a herd of hogs.
Calculate broad-sense (H²) and narrow-sense (h²) heritabilities for each trait in this herd.
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Ch. 25 - Quantitative Genetics and Multifactorial Traits
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
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Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 25, Problem 14a
A hypothetical study investigated the vitamin A content and the cholesterol content of eggs from a large population of chickens. The following variances (V) were calculated.
Calculate the narrow-sense heritability (h²) for both traits.
Verified step by step guidance1
Understand that narrow-sense heritability (h²) is the proportion of the total phenotypic variance (V_P) that is due to additive genetic variance (V_A). The formula is: \(h^{2} = \frac{V_{A}}{V_{P}}\).
Identify the values for each trait from the table: for Vitamin A, V_P = 125.5 and V_A = 12.0; for Cholesterol, V_P = 862.0 and V_A = 192.1.
Apply the formula for Vitamin A: substitute V_A = 12.0 and V_P = 125.5 into \(h^{2} = \frac{V_{A}}{V_{P}}\) to express the heritability calculation.
Apply the formula for Cholesterol: substitute V_A = 192.1 and V_P = 862.0 into \(h^{2} = \frac{V_{A}}{V_{P}}\) to express the heritability calculation.
Interpret the results by understanding that higher h² values indicate a greater proportion of phenotypic variance is due to additive genetic factors, which implies stronger potential for response to selection.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Phenotypic Variance (V_P)
Phenotypic variance represents the total observed variation in a trait within a population. It includes genetic variance (additive, dominance, etc.) and environmental variance. Understanding V_P is essential because it forms the denominator in heritability calculations, reflecting all sources of variation affecting the trait.
Recommended video:
Guided course
08:34
Analyzing Trait Variance
Additive Genetic Variance (V_A)
Additive genetic variance is the portion of genetic variance attributed to the additive effects of alleles. It is crucial for predicting response to selection because it reflects the heritable component passed from parents to offspring. Narrow-sense heritability is calculated using V_A relative to total phenotypic variance.
Recommended video:
Guided course
13:40Traits and Variance
Narrow-Sense Heritability (h²)
Narrow-sense heritability (h²) quantifies the proportion of phenotypic variance due to additive genetic variance (h² = V_A / V_P). It measures the potential for a trait to respond to selection and is key in breeding and evolutionary studies. Calculating h² requires knowledge of both V_A and V_P.
Recommended video:
Guided course
07:04Calculating Heritability
Related Practice
Textbook Question
The following variances were calculated for two traits in a herd of hogs.
Which of the two traits will respond best to selection by a breeder? Why?
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Textbook Question
The mean and variance of plant height of two highly inbred strains (P₁ and P₂) and their progeny (F₁ and F₂) are shown here.
Strain Mean (cm) Variance
P₁ 34.2 4.2
P₂ 55.3 3.8
F₁ 44.2 5.6
F₂ 46.3 10.3
Calculate the broad-sense heritability (H²) of plant height in this species.
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Textbook Question
A hypothetical study investigated the vitamin A content and the cholesterol content of eggs from a large population of chickens. The following variances (V) were calculated.
Which trait, if either, is likely to respond to selection?
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Textbook Question
In a herd of dairy cows the narrow-sense heritability for milk protein content is 0.76, and for milk butterfat it is 0.82. The correlation coefficient between milk protein content and butterfat is 0.91. If the farmer selects for cows producing more butterfat in their milk, what will be the most likely effect on milk protein content in the next generation?
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Textbook Question
In an assessment of learning in Drosophila, flies were trained to avoid certain olfactory cues. In one population, a mean of 8.5 trials was required. A subgroup of this parental population that was trained most quickly (mean=6.0) was interbred, and their progeny were examined. These flies demonstrated a mean training value of 7.5. Calculate realized heritability for olfactory learning in Drosophila.
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