Textbook Question
Which of the following traits would you expect to be inherited as quantitative traits?
Body weight in chickens
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20. Quantitative Genetics
Traits and Variance
0:57 minutesProblem 1b
Textbook Question
How can we ascertain the number of polygenes involved in the inheritance of a quantitative trait?
Verified step by step guidance1
Understand that quantitative traits are controlled by multiple genes, often referred to as polygenes, and their inheritance follows the principles of polygenic inheritance.
Recall that the number of polygenes involved in a quantitative trait can be estimated using the formula: , where 'n' represents the number of loci (genes) and the proportion of individuals in the F2 generation that resemble the parental phenotype is used to solve for 'n'.
Determine the proportion of individuals in the F2 generation that exhibit the extreme parental phenotype. This proportion is typically given in the problem or can be calculated from experimental data.
Set the observed proportion of individuals with the parental phenotype equal to and solve for 'n' using logarithmic or algebraic methods.
Interpret the value of 'n' as the minimum number of polygenes contributing to the inheritance of the quantitative trait. Keep in mind that this is an estimate and assumes equal contribution of each gene and no environmental effects.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Polygenic Inheritance
Polygenic inheritance refers to the phenomenon where multiple genes (polygenes) contribute to a single trait, often resulting in a continuous range of phenotypes. This is common in quantitative traits, such as height or skin color, where the combined effects of several alleles lead to variations in the trait's expression.
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Quantitative Traits
Quantitative traits are characteristics that are measured on a continuous scale and are influenced by multiple genes and environmental factors. Unlike discrete traits, which follow Mendelian inheritance patterns, quantitative traits exhibit a bell-shaped distribution in a population, reflecting the additive effects of many alleles.
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Statistical Methods in Genetics
Statistical methods are essential for analyzing the inheritance patterns of quantitative traits and estimating the number of polygenes involved. Techniques such as regression analysis, variance components analysis, and genome-wide association studies (GWAS) help researchers identify the genetic architecture of traits and ascertain the number of contributing genes.
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