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
Traits and Variance
Problem 1a
Textbook Question
Which of the following traits would you expect to be inherited as quantitative traits?
Body weight in chickens

1
Quantitative traits are traits that are influenced by multiple genes (polygenic inheritance) and often show continuous variation in a population, such as height, weight, or skin color.
Body weight in chickens is an example of a trait that is influenced by multiple genetic factors as well as environmental factors, making it a quantitative trait.
To determine if a trait is quantitative, consider whether it shows a range of phenotypes (e.g., a spectrum of body weights) rather than discrete categories (e.g., presence or absence of a trait).
Quantitative traits are typically analyzed using statistical methods, such as calculating the mean and variance of the trait in a population, to understand the genetic and environmental contributions.
In conclusion, body weight in chickens is expected to be inherited as a quantitative trait because it is influenced by multiple genes and environmental factors, resulting in continuous variation.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Quantitative Traits
Quantitative traits are characteristics that are influenced by multiple genes and can be measured on a continuous scale. Unlike qualitative traits, which are typically categorized into distinct groups, quantitative traits exhibit a range of phenotypes, such as height or weight. These traits are often affected by environmental factors as well, making them complex to analyze.
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Polygenic Inheritance
Polygenic inheritance refers to the phenomenon where multiple genes contribute to a single trait. Each gene may have a small additive effect on the phenotype, leading to a continuous distribution of traits in a population. For example, body weight in chickens is influenced by several genes, resulting in a range of weights rather than a few distinct categories.
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Heritability
Heritability is a measure of how much of the variation in a trait can be attributed to genetic differences among individuals in a population. It is expressed as a proportion, ranging from 0 to 1, where higher values indicate a greater genetic influence. Understanding heritability is crucial for predicting how traits like body weight in chickens may respond to selective breeding.
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Multiple Choice
The traits of an organism are controlled by its:
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