heredity, transmission from generation to generation through the process of reproduction reproduction, capacity of all living systems to give rise to new systems similar to themselves. The term reproduction may refer to this power of self-duplication of a single cell or a multicellular animal or plant organism.
..... Click the link for more information. in plants and animals of factors which cause the offspring to resemble their parents. That like begets like has been a maxim since ancient times. Although the fact of heredity has been generally known for centuries, the actual mechanisms by which inherited characteristics are transmitted to successive generations could not be satisfactorily explained until powerful enough microscopes and sufficiently refined research techniques disclosed the true nature of the universal reproductive processes of cell division and those, in "higher" animals, in which the sperm and the ovum, containing the hereditary material (see chromosome chromosome (krō`məsōm')
..... Click the link for more information. ) in their cell nuclei, unite to give rise to the new individual. Thus the science of heredity developed long after practical observations of breeding and of parent-child resemblance had been noted and also after the theory of evolution had been established. In the 18th cent. the popular concept of heredity was the theory of preformation: that the prototypical members of each organism (e.g., Adam and Eve among humans) contained within them all future generations, perfectly formed but in miniature, arranged one inside the next like a series of Chinese boxes. In the early 19th cent. Lamarck developed a theory of evolution in which the then current belief in the inheritance of acquired characteristics acquired characteristics, modifications produced in an individual plant or animal as a result of mutilation, disease, use and disuse, or any distinctly environmental influence. Some examples are docking of tails, malformation caused by disease, and muscle atrophy.
..... Click the link for more information. served as an explanation of its mechanism. The theory of pangenesis, as it was termed in a modified version in Darwinism Darwinism, concept of evolution developed in the mid-19th cent. by Charles Robert Darwin . Darwin's meticulously documented observations led him to question the then current belief in special creation of each species.
..... Click the link for more information. , was strongly reminiscent of the ideas of Hippocrates and Aristotle. It hypothesized tiny particles called pangens, or gemmules—each bearing the hereditary potential for a specific body part—which circulated in the body and eventually collected in the reproductive cells. Finally, in 1875, Oscar Hertwig's principle of the universality of fertilization in sexual reproduction confirmed the transmission of hereditary material through the two sex cells. August Weismann's theory of germ plasm continuity (1892) established that the germ (sex) cells are set apart from other body cells early in embryonic development and thus that only changes in the germ plasm, and not influences on the adult body, can affect the characteristics of future generations. In 1900 the neglected work of Gregor Mendel Mendel, Gregor Johann (grā`gôr yō`hän mĕn`dəl)
..... Click the link for more information. was rediscovered and the first scientific laws for the mechanisms of hereditary were presented. These, correlating with the microscopic and experimental observations of the behavior of chromosomes and reproductive cells and later with the biochemical analyses of genes and their products, provided the basis for modern studies. Genetics genome, or characteristic set of genes, that contains the total genetic information for an individual organism. In many familiar organisms two genes for each trait are present in each individual, and these paired genes, both governing the same trait, are called

alleles.
..... Click the link for more information. is the modern science that studies the mechanisms for the transmission of hereditary information in the resulting organism. Mutation mutation, in biology, a sudden, random change in a gene , or unit of hereditary material, that can alter an inheritable characteristic. Most mutations are not beneficial, since any change in the delicate balance of an organism having a high level of adaptation to its
..... Click the link for more information. is a mechanism for evolutionary change, initiating new variations.

Bibliography

See F. Jacob, The Logic of Life (1974); J. H. Bennett, Natural Selection, Heredity, and Eugenics (1983); B. W. Winterton, The Process of Heredity (1983).

heredity

Transmission of traits from parents to offspring through genes, the functional units of heritable material that are found within all living cells. From his studies in the mid-19th century, Gregor Mendel derived certain basic concepts of heredity, which eventually became the foundation for the modern science of genetics. Each member of the parental generation transmits only half its genes to the offspring, and different offspring of the same parents receive different combinations of genes. Many characteristics are polygenic (i.e., influenced by more than one gene). Many genes exist in numerous variations (alleles) throughout a population. The polygenic and multiple allelic nature of many traits gives a vast potential for variability among hereditary characteristics. While the genotype (an individual's total hereditary makeup) determines the broad limits of features an individual may develop, the actual features that do develop (the phenotype) are dependent on complex interactions between genes and their environment. See also variation.

heredity

1. the transmission from one generation to another of genetic factors that determine individual characteristics: responsible for the resemblances between parents and offspring

2. the sum total of the inherited factors or their characteristics in an organism

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Bibliography

heredity

heredity