Study GuideBiology–Classical (Mendelian) Genetics1. Introduction to Genetics1.1 What Is Genetics?Genetics is the study of how traits are passed from parents to their offspring. Traits are characteristicssuch as eye color, height, or earlobe shape. These traits are controlled by genes.Genes are specific sections of DNA. Each gene contains instructions for making a particular protein,and these proteins help determine how an organism looks and functions. Genes are passed from onegeneration to the next through the processes of meiosis and sexual reproduction.1.2 The Beginning of Genetics: Gregor MendelThe science of genetics began with the work ofGregor Mendel, an Augustinian monk. During the1860s and 1870s, Mendel conducted experiments that helped explain how traits are inherited.Although Mendel’s ideas were revolutionary, they were not widely accepted until the early 1900s.Today, his discoveries form the foundation of genetics. Because of this, genetics is often calledMendelian geneticsorclassical genetics. This term helps distinguish it frommolecular genetics,which focuses on DNA and genes at a chemical level.Mendel knew that “factors” were passed from parents to offspring, but he did not know these factorswere DNA. Modern science has since confirmed that genes are made of DNA and control specificinherited traits.1.3 Chromosomes, Diploid Cells, and Haploid CellsMost complex organisms, including humans, havediploid cells. A diploid cell contains two sets ofchromosomes—one set inherited from each parent.•Humans have23 pairs of chromosomes, for a total of46 chromosomes.•Because chromosomes come in pairs, diploid cells containtwo genes for eachcharacteristic.Preview Mode
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