Genetics: Reproducing Life and Producing Variation

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Copyright ©2013 W.W. Norton, Inc.

Genetics: Reproducing Life and Producing Variation

• Questions addressed in this chapter:
• What is the genetic code?
• What does the genetic code (DNA) do?
• How does understanding genes help us understand variation?

The last chapter ended with a brief introduction to DNA. But, what is DNA? What is it made of? And how can a small molecule like DNA ‘code’ for all of the traits in a living organism? We will address these and other questions in this chapter. Ultimately, what we are doing in this chapter is understanding how the genetic code (DNA) results in variation, because it is this variation that natural selection can act upon and lead to evolutionary changes. We will start by looking at the fundamental unit of all life on Earth: the cell. Inside each cell, the DNA code is structured into packages known as chromosomes. We will see how the DNA molecule can copy itself so that each cell in an organism’s body contains the same DNA information. We will then look at how DNA codes for proteins, which all living organisms are made of. Finally, we will look at a concrete example of how DNA impacts our lives by examining human blood types. Though we have to dive into the microscopic world, do not lose sight of the big picture: DNA is a code for making proteins, and we are made of proteins. If the DNA slightly changes (through mutation, which we met in the last chapter), the protein changes, and thus the organism can change.

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