Textbook Question
What advantages do cDNA libraries provide over genomic DNA libraries? Describe cloning applications where the use of a genomic library is necessary to provide information that a cDNA library cannot.
Ch. 20 - Quantitative Genetics and Multifactorial Traits
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 20, Problem 9
What kind of heritability estimates (broad sense or narrow sense) are obtained from human twin studies?
Verified step by step guidance1
Understand the difference between broad-sense heritability (H\^2) and narrow-sense heritability (h\^2). Broad-sense heritability includes all genetic variance (additive, dominance, and epistatic), while narrow-sense heritability includes only additive genetic variance.
Recognize that human twin studies typically compare trait similarities between monozygotic (identical) twins and dizygotic (fraternal) twins to estimate genetic influence on traits.
Note that because twin studies capture the total genetic contribution to trait variance (including additive and non-additive effects), the heritability estimates from these studies reflect broad-sense heritability rather than just narrow-sense heritability.
Recall that narrow-sense heritability is more specifically estimated using methods that focus on additive genetic variance, such as parent-offspring regression or SNP-based methods, which are not the primary focus of classic twin studies.
Conclude that heritability estimates from human twin studies are generally considered broad-sense heritability because they encompass all genetic variance components influencing the trait.
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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 measures the proportion of total phenotypic variance in a population that is due to all genetic factors, including additive, dominance, and epistatic interactions. It reflects the overall genetic contribution to trait variation but does not distinguish between different genetic effects.
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Calculating Heritability
Narrow Sense Heritability (h²)
Narrow sense heritability estimates the proportion of phenotypic variance attributable specifically to additive genetic variance. This measure is important for predicting the response to selection because additive effects are transmitted from parents to offspring.
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Human Twin Studies and Heritability Estimation
Human twin studies compare trait similarities between monozygotic and dizygotic twins to estimate genetic influence. These studies typically provide estimates closer to broad sense heritability because they capture all genetic effects shared by twins, not just additive genetic variance.
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Related Practice
Textbook Question
In the following table, average differences of height, weight, and fingerprint ridge count between monozygotic twins (reared together and apart), dizygotic twins, and nontwin siblings are compared:
Based on the data in this table, which of these quantitative traits has the highest heritability values?
Textbook Question
List as many human traits as you can that are likely to be under the control of a polygenic mode of inheritance.
Textbook Question
In a cross between a strain of large guinea pigs and a strain of small guinea pigs, the F₁ are phenotypically uniform, with an average size about intermediate between that of the two parental strains. Among 1014 F₂ individuals, 3 are about the same size as the small parental strain and 5 are about the same size as the large parental strain. How many gene pairs are involved in the inheritance of size in these strains of guinea pigs?
Textbook Question
Erma and Harvey were a compatible barnyard pair, but a curious sight. Harvey's tail was only 6 cm long, while Erma's was 30 cm. Their F₁ piglet offspring all grew tails that were 18 cm. When inbred, an F₂ generation resulted in many piglets (Erma and Harvey's grandpigs), whose tails ranged in 4-cm intervals from 6 to 30 cm (6, 10, 14, 18, 22, 26, and 30). Most had 18-cm tails, while 1/64 had 6-cm tails and 1/64 had 30-cm tails.
If one of the 18-cm-tail F₁ pigs is mated with one of the 6-cm-tail F₂ pigs, what phenotypic ratio will be predicted if many offspring resulted? Diagram the cross.
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Textbook Question
Erma and Harvey were a compatible barnyard pair, but a curious sight. Harvey's tail was only 6 cm long, while Erma's was 30 cm. Their F₁ piglet offspring all grew tails that were 18 cm. When inbred, an F₂ generation resulted in many piglets (Erma and Harvey's grandpigs), whose tails ranged in 4-cm intervals from 6 to 30 cm (6, 10, 14, 18, 22, 26, and 30). Most had 18-cm tails, while 1/64 had 6-cm tails and 1/64 had 30-cm tails.
Explain how these tail lengths were inherited by describing the mode of inheritance, indicating how many gene pairs were at work, and designating the genotypes of Harvey, Erma, and their 18-cm-tail offspring.
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