Heredity

By: Kaelyn Tally

Heredity Definition

Heredity is the passing of traits from parents to their offspring, either through asexual reproduction, or sexual reproduction. This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell, or organism. Genetics is the study of heredity.

Heredity Studies and Information

Geneticists found that most aspects of life have a hereditary basis, and that many traits can appear in more than one form. For instance, human beings have blond, red, brown, or black hair. They may have one of several different types of blood, one or several colors of skin. They may or may not be able to manufacture certain enzymes. Some of these traits are much more important to the life of the individual than others, but all of them are hereditary. The geneticist is interested not only in the traits of man, but in those of all other organisms as well.


The study of inheritance depends on the differences, as well as the similarities, between parents, and their offspring over many generations.


Heredity is very complex, and a geneticist cannot possibly analyze all the traits of an organism at once. Instead, he or she studies only a few traits at a time. Many other traits are present. As the geneticists work out the solution to each hereditary mystery, the geneticist must not forget that all organisms live in a complex environment. The environment may affect the degree, to which a hereditary trait develops. The geneticist must try to find out which of the many parts of the environment may affect their results.


Heredity determines what an organism may become, not what it will become. What an organism becomes, mainly depends on both its heredity and environment.


In most organisms, including man, genetics information is transmitted from mother to daughter cells and from one generation to the next by deoxyribonucleic acid, also known as DNA.

Heredity Developlment

HOW IT ALL BEGAN


The history of genetics started with the work of the Augustinian Friar Gregor Johann Mendel. His work on pea plants, published in 1866, described what came to be known as Mendelian Inheritance. In the years before, and for several decades after, Mendel's work, and wide variety of theories of heredity escalated.


THEORY OF HEREDITY


Francis Galton greeted Charles Darwin's theory of pangenesis with enthusiasm, and tried to test the assumption that the hereditary particles circulate in the blood by transfusion experiments on rabbits. The failure of these experiments led him to reject this assumption, and in the 1870s he developed an alternative theory of heredity, which incorporated those parts of Darwin's theory, that did not involve the transportation of hereditary particles throughout the system. He supposed that the fertilized ovum contains a large number of hereditary elements, a few of which are patent, developing into particular cell types, while the rest remain latent; the latent elements can be transmitted to the next generation, while the patent elements, with rare exceptions, cannot since they have developed into cells.


THE CHROMOSOME THEORY OF HEREDITY


The chromosome theory of heredity, developed in 1902–1904, became one of the foundation stones of twentieth-century genetics. It is usually referred to as the Sutton–Boveri theory after Walter Sutton and Theodor Boveri. However, the contributions of Theodor Boveri and his co-worker, Marcella O'Grady Boveri, to the understanding of heredity and development go beyond the localization of the Mendelian hereditary factors, onto the chromosomes. They investigated the interaction of cytoplasm and chromosomes, and demonstrated its relevance in heredity and development.

Augustinian Friar Gregor Johann Mendel: Developer of Heredity

Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color. With seed color, he showed that when a yellow pea and a green pea were bred together their offspring plant was always yellow. However, in the next generation of plants, the green peas reappeared at a ratio of 1:3. To explain this phenomenon, Mendel coined the terms “recessive” and “dominant” in reference to certain traits. (In the preceding example, green peas are recessive and yellow peas are dominant.) He published his work in 1866, demonstrating the actions of invisible “factors”, now called genes, in providing for visible traits in predictable ways.

Developers of Heredity Theories