Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Transgenerational epigenetic inheritance wikipedia , lookup
Genetic engineering wikipedia , lookup
Microevolution wikipedia , lookup
Genetically modified organism containment and escape wikipedia , lookup
Genetically modified crops wikipedia , lookup
Designer baby wikipedia , lookup
During the 1860' s, an Austrian monk and biologist named Gregor Mendel worked among hundreds of pea plants in the garden of a small monastery in Czechoslovakia. Mendel experimented with pea plants to seeif he could fmd a pattern in the way certain characteristics are handed down from one generation of pea plants to the next generation. Another word for the characteristics of an organism is trait. So Mendel actually studied the way certain traits are passedon from one generation of organisms to the next generation. Pea plant traits include how tall the plant grows, the color of their seeds,and the shape of their seeds. Although Mendel 4id not realize it at the time, his experiments would come to be consideredthe beginning of genetics. Genetics is the study ofheredity, or the passing on of traits from an organism to its offspring. F or this reason, Mendel is called the Father of Genetics. Mendel chose pea plants for his experiments becausepea plants grow and reproduce quickly. So he knew that he could study many generations of pea plants in a short amount of time. Mendel also knew that pea plants had a variety of different traits that could be studied at the sametime. That is, he could study plant height, plant seed color, plant seed shape and other traits in the sameexperiment. At first, Mendel was bewildered by the behavior of certain traits of pea plants. For example, when he grew pea plant from seeds produced by certain tall pea plants that he had pollinated with pollen from short pea plants, Mendel expected all of the offspring to be of medium height. Instead, all of the offspring were tall. Every time he repeatedthis procedure ~ v ~ . -- , , These pea plants display the ideal ratio of tall to short plants for offspring of parents that each had a dominant and recessive gene for height. with the same plants, he got the same results. It seemedthat there was something about the tall trait that overwhelmed, or dominated, the short trait. Mendel called this stronger trait the "dominate trait." He called the trait that was dominated the "recessive trait," becauseit seemedto recede, or vanish. Mendel then decided to try something different. He took a group of the tall offspring and cross pollinated them. He harvested the seedsand replanted them. Surprisingly, he found some short pea plants among the offspring. Mendel detected a pattern to his results that helped him to recognize some of the fundamental principles of heredity. Mendel was convinced that the male and the female pea plant each contributed something during fertilization that helped determine a trait. Since each parent contributed ~ something, he concluded that there had to be a ., -., for be talloi --, that these ..somethings" that Mendel observed in are each determined by a pair of genes -one gene from the male and one from the female. Mendel used upper caseletters to represent the dominant gene. For example, he used '.r' as the symbol for the tallness gene in pea plants. He used a lower case.'t" as the symbol for shortness in pea plants. Mendel believed that whenever an organism expresses, or displays, a dominant trait, at least one dominant gene must be present,F or example, if a pea plant is tall, its gene pair has to be either '.TT" or "Tt."