How Genes Effect Our Appearance essays

How Genes Effect Our Appearance essays In 1865, an Augustinian monk named Gregor Mendel discovered that individual traits are determined by discrete "factors," later known as "genes," which are inherited by the parents. While researching his new discovery, he found that genes come in pairs, and each gene has a trait with two alternate forms, such as the pea plant with it's green or yellow seeds. By analyzing the results of various crosses, Mendel concluded that each alternative form of a trait is specified by alternative forms of a gene. To follow the inheritance from parent to child, Mendel first needed to be sure which genes each parent carried. Since pea plants are naturally self-fertilizing, "pure-bred" strains were available. Upon closer look, Mendel discovered that each strain contained only one form of the gene that determined a trait. From the results of further experiments, Mendel theorized that pure-bred plants must have two copies of the same gene for each trait. In general, offspring appear to be a mixture of parental characteristics. However, Mendel found that this is not true for the pea plant traits that he chose to study. Pure-bred pea plants when crossed did not produce offspring with blended traits. For example, one might expect that when a pure-bred green-seeded and a pure-bred yellow-seeded pea plant were crossed their offspring would produce seeds with a green-yellow color. That, however, was not true for everytime only one color was produced: yellow. There were no blends present, and the green color disappeared. Mendel proposed that although both gene alternates are present, there is no blending of color because the gene alternate for yellow is dominant over the gene alternate for green. The dominant trait is seen only when a single copy of it's gene is inherited. When he crossed the hybrid offspring, green seeds reappeared in the next generation. Mendel theorized that the recessive green trait is shown onl ...