In this chapter, we focused on a mode of inheritance referred to as quantitative genetics, as well as many of the statistical parameters utilized to study quantitative traits. Along the way, we found opportunities to consider the methods and reasoning by which geneticists acquired much of their understanding of quantitative genetics. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:
How do we know that monozygotic twins are not identical genotypically as adults?
Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
20. Quantitative Genetics
Heritability
Problem 13Klug - 12th Edition
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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1
Identify the formula for broad-sense heritability: H^2 = \frac{V_G}{V_P}, where V_G is the genetic variance and V_P is the phenotypic variance.
Determine the phenotypic variance (V_P) from the F2 generation, which is given as 10.3.
Calculate the genetic variance (V_G) using the formula V_G = V_P - V_E, where V_E is the environmental variance.
Estimate the environmental variance (V_E) by averaging the variances of the parental strains P1 and P2: V_E = \frac{4.2 + 3.8}{2}.
Substitute the values of V_G and V_P into the heritability formula to find H^2.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Broad-Sense Heritability (H²)
Broad-sense heritability (H²) is a measure of the proportion of phenotypic variance in a trait that can be attributed to genetic variance among individuals in a population. It encompasses all genetic contributions, including additive, dominance, and interaction effects. H² is calculated using the formula H² = VG/VP, where VG is the genetic variance and VP is the total phenotypic variance. Understanding H² is crucial for predicting how traits may respond to selection.
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Phenotypic Variance (VP)
Phenotypic variance (VP) refers to the total variance observed in a trait within a population, resulting from both genetic and environmental factors. It can be partitioned into genetic variance (VG) and environmental variance (VE). In the context of the question, calculating VP involves summing the variances of the parental strains and their progeny, which helps in understanding the overall variability in plant height.
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Genetic Variance (VG)
Genetic variance (VG) is the portion of phenotypic variance that is attributable to genetic differences among individuals. It can be further divided into additive genetic variance (the cumulative effect of individual alleles) and non-additive genetic variance (due to interactions between alleles). In calculating broad-sense heritability, accurately estimating VG is essential, as it directly influences the heritability of traits like plant height.
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