All genes shown in upper case are dominant. All recessive genes are given in lower case. This case distinction between the dominant and recessive types is a standard practice to aid in keeping them properly classified in ones mind. Just remember, if its listed as beginning with a capital letter, it's a dominant gene. A dominant gene will always express itself when not being masked by another, more dominant or modifying type gene.
Symbols beginning in lower case are always recessive.
They can only be displayed when in their pure state. Chromosomes come in pairs, their genes may or may not come in matching sets. When each of the set is identical in type they are said to be pure for that gene type. In the case of recessive genes, they will only express themselves when in this pure state. A combination of one recessive and one dominant results in the more dominant one of the set being expressed.