Added Lecture notes about variance.

 

See Box 9C in your text book and the tail end of notes from Lecture 14.

 

How can we understand polygenic traits?

1.   Think in terms of variances

2.   Two descriptors:

a.       Mean

b.      Variance

  1. Phenotype is a function of genetic and environmental sources of variance
  2. Heritability describes the proportion of phenotypic variance that is from genetic sources

How do we separate VG from VE?

  1. Two ways
    1. Resemblance among relatives

                                                               i.      More closely related, the greater the expected resemblance

                                                             ii.      Comparison is often between parents and offspring

                                                            iii.      Slope is the heritability

                                                           iv.      Two hypothetical extreme cases

    1. Artificial selection

A more realistic example

  1. Heritability of height of students in an Evolution course at Pacific Northwest