Childhood is the culturally defined period in human development between infancy and adulthood. In a historical perspective, this is a relatively new social construction. Early childhood, as an especially important "superperiod" of childhood, most often refers to the months and years between infancy and school age children. To understand why childhood is such a crucial time in human life it is important to study the development before and after birth along with any factors that may alter life in between. Heredity is the transmission of characteristics for parents to offspring through genes. Genes are information carriers. There are two types of genes, dominant and recessive. Dominant genes will emerge each time they are present. A recessive gene will only appear when paired with another recessive gene. These genes make each person unique. They determine what color hair and eyes you will have, your body type, and possible even your personality. A problem can take place in any pregnancy. Such problems can be caused by fate or by fault. Genetic problems are cause by a natural defect in the genes, which are inherited by the offspring's parents. These defects can result in a number of diseases. Cystic fibrosis, Tay-Sachs disease, and sickle-cell anemia are examples of this type of abnormalities. It can be said that genetics is all a roll of the dice.
Fortunately, through modern science, many of these defects can be diagnosed through prenatal testing. The invention and use of the ultrasound has made obstetrics a more precise science pregnancy a much less worrisome experience. In fact, ultrasounds have become so common that they are now used in ninety percent of pregnancies today. It is so common because it allows visualization of the fetus without the hazards of x-ray. Ultr ...