(http://www.nature.com/scitable/topics)
(http://www.nature.com/scitable/course-cover/Essentials-of-Genetics-8)
What smaller elements make up the complex DNA molecule, how are these elements arranged, and how is information extracted from them? This unit answers each of these questions, and it also provides a basic overview of how DNA was discovered.
The passage of DNA from one cell to another is the basic means by which genetic information — and therefore biological characteristics — can persist relatively unchanged across millions of generations of organisms. The mechanism by which DNA is passed from one generation of cells to the next is a combination of DNA replication and cell division. In this unit, you will learn how DNA is first packaged and then passed on to the next generation during cell division. You will also explore the unpredictable ways in which DNA can change during this process.
Heredity, or the continuity of traits between parent and offspring, is powered by the physical transmission of DNA between cells during reproduction. In this unit, you will learn about the origins of our modern understanding of heredity, as well as the basic rules that determine how parents’ traits determine the traits of their offspring.
Although DNA is so extremely small that we are not able to see it with the naked eye, scientists have developed laboratory techniques to track DNA and even modify it. With these techniques, scientists can assess how active gene transcription is, and what conditions can change it. Scientists can also ask fundamental questions about multiple genes at the same time. In this unit, you will learn what these techniques are, how they are performed, and what they achieve.
Because DNA passes from parent to offspring, there is generally significant genetic similarity between the organisms in a population, provided that the members of this population have descended from common ancestors. For example, although human beings have existed for 200,000 years, there is a less than 0.1% difference (called genetic variability) between the DNA of even the most dissimilar human beings. Nonetheless, the collective genetic makeup of entire populations can change significantly over time. The study of how this happens among both humans and other organisms is called population genetics. In this unit, you will learn how the underlying genetic variability of a population emerges, as well as how and why the collective genetic makeup of a population can change.