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| Gregor Mendel was the first person to trace the characteristics of successive generations of a living organism. He was an Augustinian monk who taught natural science to high school students. His origins were humble. However, his work was so brilliant that it took many years for the rest of the scientific community to catch up to it. |
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The modern science of genetics started with the work of Gregor Mendel. He found that certain factors in a plant cell determined the traits a plant would have. Thirty years after his discovery these factors were given the name genes. Of the traits that Mendel studied, he found that one factor, or gene, could mask the effect of another. This is the principle of dominance. He called the factor that showed up in the offspring dominant, and the factor that was masked recessive.
Genotype refers to the genes that an organism contains for a particular trait. The phenotype is the observable traits of an individual. Phenotype is a product of the interaction between the genotype and the environment.
All genes interact with the environment. Sometimes it is difficult to tell how much of a phenotype is determined by heredity and how much is influenced by the environment. A familiar example of how the environment affects the phenotype is the coloring of Siamese cats.
The cats have a genotype for dark fur. However, the special proteins (enzymes) that produce the dark color work best at low temperatures. That is why Siamese cats have dark markings on their ears, nose, paws, and tail. These are all areas that have a low body temperature. Suppose a Siamese cat’s tail were shaved and then kept at a higher than normal temperature. It would soon be covered with light-colored fur. |
Bio Words
dominant: used to describe the gene that determines the expression of a genetic trait; the trait shows up recessive: used to describe the gene that is overruled by a dominant gene; the trait is masked genotype: the genes of an individual phenotype: the observable traits of an organism that result because of the interaction of genes and the environment |
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