Biology- Inheritance and Genetic Diagrams

How many copies of a gene are there and how many are expressed?

What is homozygous?

What is heterozygous?

What can alleles be? (two different types).

How many alleles must be present for a dominant allele to be expressed?

Who many alleles must be recessive for it to be expressed?

What case of letter are dominant and recessive alleles represented by?