Mendelian and Molecular Genetics
The word inheritance usually brings to mind money or propertyleft by a relative who has passed away. But there’s another type ofinheritance that is right under our noses—actually, your nose is partof the inheritance. Every living organism has characteristics orfeatures that it passes on to its offspring. These tendencies of heredityare obvious: even a child knows cows give birth only to other cows, andthat children often look like their parents. But, in fact, the specificbiological mechanisms that allow parents to transmit their features totheir offspring were an enormous mystery until about 140 years ago.Scientists back then knew that parents somehow made a tiny copy ofthemselves inside an egg or a sperm, but they had no idea what thesecopies were or how they worked.
Then, in the 1860s, an Austrian monk named Gregor Mendelstarted breeding peas in his garden. Where others saw only plants,Mendel looked deeper and found the basic units of heredity we now call genes.If you remember from the last chapter, genes are the parts of achromosome that are transcribed to mRNA and are ultimately translatedto the proteins essential to cellular processes. Mendel had noknowledge of protein synthesis and had never seen a chromosome, but hissimple experiments with peas and the laws he developed to describe thebehavior of hereditary—now termed classical genetics—have provided thefoundation for the modern field of molecular genetics, the study ofheredity on the molecular level.
For the SAT II Biology, you need a solidunderstanding of the basic laws and patterns of both classical geneticsand molecular genetics. Questions on genetics can make up anywhere from14 to 20 percent of the core of the SAT II Biology. In addition, the“M” section of the Biology E/M test focuses on evolution in terms ofmolecular biology, including genetics.
