In this chapter, we will begin by examining some of how heredity helps to shape the way we are.  We will look at what happens genetically during conception, and describe some known genetic and chromosomal disorders.  Next, we will consider what happens during prenatal development, including the impact of teratogens.  We will also discuss the impact that both partners (e.g., mother and father) have on the developing fetus.  Next, we will present the birth process and some of the complications that can occur during delivery.  Before going into these topics, however, it is essential to understand how genes and chromosomes affect development.