Evolutionary relationships between genes

[Arthur Wohlwill]

Can anyone recommend a good reference that discusses how to analyze the 
evolutionary relationships bewteen genes from different organisms?  
Specifically, I need to get correct definitions for homologous, orthologous 
and paralogous genes. I also need to know the correct way to describe a 
situtation in which one organism has a single gene, but a higher organism has 
multiple related genes.  Is it proper to to call the single gene the 
"homologue" of the cluster of related genes? Thank you very much,

Arthur Wohlwill adwohlwi at UIC.EDU