Amy Price, age 14, of Dayton, Ohio, for her question:
WHO DISCOVERED GENETICS?
Genetics is the study of heredity, the passing on of characteristics from parents to their offspring. The principles of genetics were discovered by an Austrian monk named Gregor Mendel during the 1860s. Mendel found that garden peas inherited various traits in a predictable manner. He decided that many characteristics are passed on from generation to generation by factors that are now called genes.
Genes are present in the cells of all organisms. Genes determine most physical traits, such as general body build and the color of the eyes, hair and skin.
Mendel discovered that organisms inherit two. forms of the gene for each trait, one from each parent. Mendel's work remained unnoticed until the early 1900s when genetics became a recognized science.
About 1910, an American biologist named Thomas Hunt Morgan discovered that genes are located on cell structure called chromosomes. All the genes on one chromosome are called linked genes. In most cases, linked genes are inherited together.
Later Morgan found that offspring sometimes inherit only some of the genes on a chromosome. He concluded that genes occasionally cross over from one chromosome to another. A Dutch botanist named Hugo DeVries found early in the 1900s that certain organisms had characteristics that were not present in their ancestors. These differences, which are caused by changes in the genes, are called mutations.
A new type of plant or animal that results from mutations is called a mutant. If the mutated genes are present in the organism's sex cells, they will be transmitted to the offspring.
In 1927, an American geneticist named Hermann Muller discovered that artificial mutations could be produced by treating an organism with X rays.
During the 1940s, two American geneticists studied the relationship between genes and chemical activity in cells. They were George Beadleand Edward Tatum. They concluded that genes control the production of enzymes, proteins that speed up and direct the cell's chemical reactions.
Scientists also discovered during the 1940s that, in a large majority of organisms, genes consist of a substance called deoxyribonucleic acid. This material is called DNA. DNA serves as a blueprint for the construction of protein molecules in cells.
Today, geneticists are particularly concerned with the fields of population genetics and molecular genetics.
Population geneticists study how various factors affect the frequency of various genes in humans, animals and plants. These data provide much information about genetic diseases.
Molecular genetics study the chemical composition of DNA. They examine how DNA controls the activity of cells and transmits characteristics from generation to generation.