biology pdf

Key Concepts ? Inherited traits are affected by genes. ? Genes are composed of the chemical deoxyribonucleic acid (DNA). ? DNA replicates to form (usually identical) copies of itself. ? DNA contains a code specifying what types of enzymes and other proteins are made in cells. ? DNA occasionally mutates, and the mutant forms specify altered proteins. ? A mutant enzyme is an ?inborn error of metabolism? that blocks one step in a bio- chemical pathway for the metabolism of small molecules. ? Traits are affected by environment as well as by genes. ? Organisms change genetically through generations in the process of biological evolution. ? Because of their common descent, organisms share many features of their genetics and biochemistry. Key Terms