Introduction
Mendel was able interpret the results of his genetic crosses because he took
careful notes, made accurate counts, and chose traits that exhibited a clear
dominant or recessive expression pattern. In fact, alleles that show simple
dominant or recessive expression patterns are sometimes called "Mendelian
traits". Many alleles, however, do not behave in such a simple Mendelian
manner. This tutorial will explore more complex patterns of expression as well
as the application of genetic principles to the development of pedigrees.
The Learning Objectives for this tutorial are that by the end of this tutorial, you should be able to:
- Explain the purpose of a pedigree and be able to read and interpret a pedigree chart
- Construct a pedigree given sufficient information
- Make predictions about future offspring based on the information in a pedigree
- Identify the different patterns of inheritance seen in humans using specific genes (cystic fibrosis, PKU, sickle cell anemia, and Huntington’s)
- Perform genetic crosses involving genes with multiple alleles
- Compare and contrast the different dominance relationships that alleles can show
- Discuss the phenomenon of pleiotropy and its effect on an organism’s phenotype
- Explain how epistasis affects the expression of genes
- Describe polygenic inheritance