Assignment: Quality Improvement Action Plan

The Minnesota study of identical twins points to both the importance of the genetic basis of

human development and the need for further research on genetic and environmental factors.

The examples of Jim and Jim and the giggle sisters stimulate us to think about our genetic

heritage and the biological foundations of our existence. Organisms are not like billiard balls,

moved by simple, external forces to predictable positions on life’s pool table. Environmental

experiences and biological foundations work together to make us who we are. Our coverage of

life’s biological beginnings and experiences will emphasize the evolutionary perspective; genetic

foundations; the interaction of heredity and environment; and charting growth from conception

through the prenatal period, the birth process itself, and the postpartum period that

follows birth. ■

Genetic Foundations of Development Genetic influences on behavior evolved over time and across many species. Our many traits and characteristics that are genetically influenced have a long evolutionary history that is retained in our DNA. In other Page 39 words, our DNA is not just inherited from

our parents; it’s also what we’ve inherited as a species from the species that came before our own. Let’s take a closer look at DNA and its role in human development. How are characteristics that suit a species for survival transmitted from one generation to the next? Darwin did not know the answer to this question because genes and the principles of genetics had not yet been discovered. Each of us carries a human “genetic code” that we inherited from our parents. Because a fertilized egg carries this human code, a fertilized human egg cannot grow into an egret, eagle, or elephant.

Each of us began life as a single cell weighing about one twenty-millionth of an ounce. This tiny piece of matter housed our entire genetic code—instructions that orchestrated growth from that single cell to a person made of trillions of cells, each containing a replica of the original code. That code is carried by our genes. What are genes and what do they do? For the answer, we need to look into our cells.

The nucleus of each human cell contains chromosomes, which are threadlike structures made up of deoxyribonucleic acid, or DNA. DNA is a complex molecule that has a double helix shape, like a spiral staircase, and contains genetic information. Genes, the units of hereditary information, are short segments of DNA, as you can see in Figure 2. They help cells to reproduce themselves and to assemble proteins. Proteins, in turn, are the building blocks of cells as well as the regulators that direct the body’s processes (Cowan, 2015; Goodenough & McGuire, 2017).