Lecture 22 - Quantitative Genetics 06-12-11

Lecture 22 - Quantitative Genetics 06-12-11 - Lecture 22...

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Quantitative Genetics Lecture 22 June 13, 2011 Chapter 24 1. Quantitative traits 2. Analysis of quantitative traits 3. Heritability of quantitative traits
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Qualitative Traits ¾ Eg. pea seed shape, pea flower color, height, “This or that” phenotypes ¾ Simple relationship between genotype and phenotype. Up to this point we have studied traits under the control of one or two genes Distinct phenotypes or classes (discontinuous characteristic) Known as qualitative traits
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Quantitative Traits Influenced by multiple genes and the environment. ¾ Eg. grain yield, animal weight, milk production, seed oil content, plant maturity ¾ Complicated relationship between genotype and phenotype. Many traits show continuous variation. ¾ Can’t be separated into distinct types. ¾ Known as quantitative traits (polygenic traits, multiple factor traits, or complex traits).
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How Quantitative Traits Inherited? Kernel color in wheat - 2 pairs of incomplete dominant genes Nilsson-Ehle’s cross
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Inheritance of quantitative traits is the accumulative affects of multiple genes, each following Mendel’s rules with small effects. (1/4) n is individual number in the F 2 that resemble original homozygous parent. n= number of loci How Quantitative Traits Inherited?
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Quantitative Genetics No distinct phenotypes – continuous. ¾ Mendelian analysis cannot be applied. Statistical methods are used to describe and analyze quantitative traits. Quantitative Genetics: The study of the inheritance of quantitative traits. ¾ Determine how the genotype and environment interact to produce a trait with a continuous distribution.
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Analysis of Quantitative Traits Frequency Distribution Description of the numbers and kinds of phenotypes present in a population. A graph of the frequencies (numbers or proportions) of the different phenotypes. Two major features of distribution are the mean and variance .
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Mean (average ), provides the information about the center of the distribution curve. Calculation: the total of individual measurements divided by the total number of observations (n). x
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Lecture 22 - Quantitative Genetics 06-12-11 - Lecture 22...

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