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
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

20. Quantitative Genetics

Traits and Variance

Genetics

20. Quantitative Genetics

Traits and Variance

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1:54 minutes

Problem 1b

Textbook Question

Which of the following traits would you expect to be inherited as quantitative traits?
Growth rate in sheep

Verified step by step guidance

Understand the concept of quantitative traits: Quantitative traits are traits that are influenced by multiple genes (polygenic inheritance) and often show a continuous range of variation. Examples include height, weight, and growth rate.

Recognize that growth rate in sheep is likely influenced by multiple genetic factors as well as environmental factors, making it a quantitative trait.

Consider the characteristics of quantitative traits: They are typically measured and expressed numerically, such as in units of growth per day or weight gain over time.

Compare growth rate in sheep to other traits that are qualitative (e.g., coat color, which is often controlled by a single gene and shows discrete categories). This distinction helps confirm that growth rate is quantitative.

Conclude that growth rate in sheep is inherited as a quantitative trait because it is influenced by multiple genes and shows a range of phenotypic variation rather than discrete categories.

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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, such as height, weight, or growth rate. Unlike qualitative traits, which are typically categorized into distinct classes, quantitative traits exhibit a range of phenotypes due to the additive effects of several alleles. This complexity makes them subject to environmental influences as well.

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, growth rate in sheep is likely influenced by several genes, making it a polygenic trait that can vary widely among individuals.

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 contribution to the trait. Understanding heritability is crucial for predicting how traits like growth rate in sheep can be passed on to future generations.

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Related Practice

Multiple Choice

A trait controlled through polygenic inheritance was observed in a series of experiments. A brown eyed rabbit was mated with a blue eyed rabbit. 130 F2 offspring were produced. 2 offspring had brown eyes and 2 offspring had blue eyes. How many polygenes control eye color in rabbits?

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