The importance of Genetics
Alexis's hemophilia illustrates the important role that genetics plays in a person's life. A difference in one gene, of the 20,000 to 25,000 genes that each human possesses, changed Alexis's life, affected his family, and perhaps even altered the course of history. We all possess genes that influence our lives. They affect our height, weight, hair color, and skin pigmentation. They influence our susceptibility to many diseases and disorders and even contribute to our intelligence and personality. Genes are fundamental to who and what we are.
The Role of Genetics in Biology Genetics provides one of biology's unifying principles: all organisms use the same genetic system. Genetics also undergirds the study of many other biological disciplines. Evolution s genetic change taking place through times; so the study of evolution requires an understanding of basic genetics.
Genetic Diversity and Evolution Life of Earth exists in tremendous array of forms and features that occupy almost every conceivable environment. Life is also characterized by adaptation: many organisms are exquisitely suited to the environment in which they are found. The history of life is a chronicle of new forms of life emerging, old forms disappearing, and exiting forms changing. Despite their tremendous diversity, living organisms have an important feature in common: all use the same genetic system. A complete set of genetic instructions for any organism is its genome, and all genomes are encoded in nucleic acids-either DNA or RNA.
Divisions of Genetics Traditionally, the study of genetics has been divided into three major subdisciplines: transmission genetics, molecular genetics, and population genetics. Transmission genetics encompasses the basic principles of genetics and how traits are passed from one generation to the next. Molecular genetics concerns the chemical nature of the gene itself: how genetic information is encoded, replicated, and expressed. It includes the cellular processes of replication, transcription, and translation-by which genetic information is transferred from one molecule to another- and gene regulation -the processes that control the expression of genetic information. Population genetics explores the genetic composition of groups of individual members of the same species and how that composition changes over time and geographic space.