heredity

heredity,

transmission from generation to generation through the process of reproductionreproduction,
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 chromosomechromosome
, structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome
..... 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 characteristicsacquired 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 DarwinismDarwinism,
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 MendelMendel, Gregor Johann
, 1822–84, Austrian monk noted for his experimental work on heredity. He entered the Augustinian monastery in Brno in 1843, taught at a local secondary school, and carried out independent scientific investigations on garden peas and other plants until
..... 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. Geneticsgenetics,
scientific study of the mechanism of heredity. While Gregor Mendel first presented his findings on the statistical laws governing the transmission of certain traits from generation to generation in 1856, it was not until the discovery and detailed study of the
..... Click the link for more information. is the modern science that studies the mechanisms for the transmission of hereditary information in the resulting organism. Mutationmutation,
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 environment
..... 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

the property characteristic of all living organisms, by which identical traits and developmental characteristics are repeated in a number of generations. Heredity depends on the transmission from one generation to another during reproduction of the material structures of the cell that contain programs for the development of new individuals.

The continuity of the morphological, physiological, and biochemical organization of living things and the character of their individual development, or ontogeny, are ensured by heredity. As a general biological phenomenon, heredity is the most important condition for the existence of differentiated forms of life. Different species would be impossible without a relative continuity in the traits of organisms, even though this continuity is disrupted by mutation, which gives rise to intraspecies differences between organisms. Embracing the most varied traits in all stages of ontogeny, heredity is manifested in the laws of inheritance of traits—that is, in the principles governing the transmission of characteristics from parents to offspring.

The term “heredity” is sometimes applied to the transmission from generation to generation of infectious principles (infective heredity) or of learning skills, education, and traditions (social or signal heredity). However, the broadening of the concept of heredity beyond its biological and evolutionary essence is debatable. Only in cases where infectious agents are capable of interacting with the host cells to the point where they are incorporated into their genetic apparatus is it difficult to separate infective from normal heredity. Conditioned reflexes are not inherited but are developed by each generation, although heredity undoubtedly plays a role in the speed with which they and various behavioral characteristics are reinforced. Thus, biological heredity is a component of social heredity.

Explanations of the phenomena of heredity that date from antiquity (Hippocrates, Aristotle) are only of historical interest. Until the discovery of sexual reproduction, the concept of heredity could not be accurately defined and linked with certain parts of the cell. Data on the laws of heredity were obtained by the mid-19th century from numerous experiments with plant hybridization (for example, J. G. Kölreuter’s work). In 1865, G. Mendel published a clear, mathematical generalization of the results of his experiments on the hybridization of peas. These generalizations were subsequently called the Mendelian laws, and they became the foundation of Mendelism, the teaching on heredity. At about the same time, attempts were made to gain a theoretical understanding of heredity. In the book The Variation of Animals and Plants Under Domestication (1868), C. Darwin advanced his “provisional hypothesis of pangenesis,” according to which the rudiments of all the cells of the organism (the gemmules) separate from the cells and, moving through the bloodstream, settle in the sex cells or in structures involved in asexual reproduction, such as buds. This implies that the sex cells and buds consist of a vast number of gemmules. When the organism develops, the gemmules are transformed into the same type of cells from which they were formed. The pangenesis hypothesis combined ideas of unequal value: the concept of the presence in the sex cells of special particles that determine the subsequent development of the individual, and the notion that these particles are transported from the somatic to the sex cells. The concept of special particles was correct and led to modern ideas regarding corpuscular heredity. But the second notion, which laid the foundation for the idea of the inheritance of acquired characteristics, was wrong. F. Galton, K. W. von Nageli, and H. de Vries also elaborated speculative theories of heredity.

The most detailed speculative theory of heredity was proposed in 1892 by A. Weismann. Drawing on the information then available on fertilization, he recognized the presence in the sex cells of a special substance, a carrier of heredity, or germ plasm. Weismann regarded the visible structures in the cell nucleus, the chromosomes (idants), as the highest units of germ plasm. According to his theory, idants consist of ids arranged in a line of granules. Ids consist of determinants, which determine the various kinds of cells that arise during the development of the individual, and biophores, which are responsible for the individual properties of the cells. An id contains all the determinants needed to construct the body of an individual of a given species. Germ plasm is found only in sex cells, not in somatic, or body, cells. To account for this radical difference between the two types of cell, Weismann assumed that during the cleavage of a fertilized egg, the main supply of germ plasm (that is, of determinants) enters one of the first cleavage cells, which becomes the parent cell for embryonic development. Only some of the determinants enter the remaining cells of the embryo during “unequal inheritance divisions.” Finally, the cells contain determinants of one kind, which determine their nature and properties. The essential property of germ plasm is its great continuity. Although Weismann’s theory was erroneous in many details, his idea concerning the role of chromosomes and the linear arrangement of the elementary units of heredity proved to be correct and anticipated the chromosomal theory. The logical conclusion to be drawn from Weismann’s theory is that acquired characteristics are not inherited.

All the speculative theories of heredity contained some elements that were subsequently confirmed and more fully developed in the science of genetics, which developed in the early 20th century. Among the most important contributions of the speculative theories is the concept of the segregation in the organism of individual traits or properties, the inheritance of which can be analyzed by appropriate methods, and the idea that these properties are determined by special, discrete units of heredity localized in a cell structure (the nucleus). Darwin called these units gemmules; de Vries, pangenes; and Weismann, determinants. The term “gene,” which was suggested by W. Johannsen in 1909, is widely accepted in contemporary genetics.

Attempts to discover the laws of heredity by using statistical methods fall into a special category. F. Galton, one of the founders of biometrics, used statistics to calculate correlations and regressions in order to establish the relationship between parents and offspring. He formulated a number of laws of heredity (1889), including atavism, or a throwback to the organism’s ancestors, and ancestral heredity, or the share of ancestral heredity in the heredity of the offspring. The laws are statistical, apply only to populations of organisms, and do not reveal the essence and causes of heredity, which could be disclosed only by the experimental study of heredity by different methods, especially hybrid analysis, the foundations of which were laid by Mendel.

The laws of inheritance of qualitative characteristics assert that in a monohybrid, the difference between crossed forms depends on only one pair of genes; in a dihybrid, on two; and in a polyhybrid, on many. Analysis of the inheritance of quantitative characteristics failed to provide a clear-cut picture of segregation. This led to the identification of a special, “blending inheritance,” which was explained by the mixing of the inherited plasms of the crossed forms. Subsequently, hybrid and biometric analysis of the inheritance of quantitative characteristics showed that even blending inheritance involves discrete traits, and inheritance of quantitative traits is polygenic. In polygenic inheritance it is difficult to detect segregation, because of the involvement of many genes whose effect on a trait is complicated by the strong influence of environmental conditions. Thus, although traits can be categorized as qualitative or quantitative, the terms “qualitative” and “quantitative” heredity are not justified, because both types of heredity are fundamentally the same.

The development of cytology led some scientists to raise the question of the material basis of heredity. Relying on their study of fertilization, O. Hertwig (1884) and E. Strasburger (1884) were the first to suggest that the nucleus functions as the carrier of heredity. T. Boveri (1887) discovered the individuality of chromosomes and hypothesized that they were qualitatively different. He and E. van Beneden (1883) observed that the number of chromosomes is halved during the formation of sex cells in meiosis. The American scientist W. Setton (1902) offered a cyto-logical explanation of Mendel’s law of the independent inheritance of traits. The chromosomal theory of heredity was substantiated beginning in 1911 by T. H. Morgan and his school, who demonstrated an exact correlation between the genetic and cytological data. In experiments on the fruit fly Drosophila they found an exception to the independent distribution of characters —linked inheritance, a phenomenon explained by the linkage of genes, or the location of the genes responsible for a particular trait on a single pair of chromosomes. Study of the frequency of recombinations between linked genes as a result of crossing-over made it possible to construct maps showing the location of genes on the chromosomes. The number of groups of linked genes equalled the number of pairs of chromosomes in a given species.

The most important evidence supporting the chromosomal theory of heredity came from a study of sex-linked inheritance. In the chromosome sets of several animal species cytologists discovered special sex chromosomes that distinguished females from males. In some cases the females have identical sex chromosomes (XX), and the males have different ones (XY). In other cases the males have two identical chromosomes (XX or ZZ), and the females have different ones (XY or ZW). The sex with identical sex chromosomes is called homogametic, and the sex with different ones, heterogametic. In some insects, including Drosophila, and in all mammals the females are homogametic, and the males, heterogametic. The opposite is true in birds and butterflies. In the fruit fly Drosophila the inheritance of several traits is associated strictly with the transmission of X chromosomes to the offspring. The female fly, for example, can carry a recessive gene for white eyes. Because the female fly is homozygous for this gene, which is located on the X chromosome, white eyes are transmitted to all the male offspring, who obtain their X chromosome from their female parent. If the female parent is heterozygous for a recessive sex-linked gene, the trait is transmitted to half the male progeny. In species where the males are homogametic (XX or ZZ) and the females heterogametic (XY or ZW), the males transmit sex-linked traits to their female offspring, who obtain their X (or Z) chromosome from the male parent.

Sometimes XXY females and XYY males appear as a result of the nondisjunction of sex chromosomes. It is also possible for X chromosomes to be joined at the ends. In this case, the females transmit linked X chromosomes to their female offspring, in whom sex-linked traits are expressed, but the male offspring are like the male parent (hologenic inheritance). If the inherited genes are located on the Y chromosome, the traits determined by them are transmitted only through the male line, from father to son (holandric inheritance). The chromosomal theory uncovered the intracellular mechanisms of heredity, provided an accurate and consistent explanation for all the phenomena of inheritance in sexual reproduction, and accounted for changes in heredity—that is, mutation.

The paramount role of the nucleus and chromosomes in heredity does not preclude the transmission of some traits through the cytoplasm, which contains structures capable of replication (cytoplasmic heredity). Units of cytoplasmic (non-chromosomal) heredity differ from those of chromosomal heredity in that they do not separate during meiosis. Therefore, in nonchromosomal heredity the offspring reproduces the traits of only one of the parents (generally the female). Thus, a distinction is made between nuclear heredity (sometimes called chromosomal heredity), which is associated with the transmission of hereditary traits located in the chromosomes of the nucleus, and extranuclear heredity, which depends on the replication of structures in the cytoplasm. Nuclear heredity is also associated with vegetative (asexual) reproduction, but it does not result in the redistribution of genes that occurs in sexual reproduction. It ensures a constant transmission of traits from generation to generation that is disrupted only by somatic mutations.

The availability of new physical and chemical methods, as well as the use of bacteria and viruses in research, sharply increased the capacity of genetic experiments to solve problems and led to the study of heredity at the molecular level and the rapid development of molecular genetics. N. K. Kol’tsov was the first to advance and substantiate the idea that heredity has a molecular basis. He proposed the matric method of reproducing “hereditary molecules” (reported in 1927 and published in 1928 and 1935). The genetic role of deoxyribonucleic acid (DNA) was experimentally demonstrated in the 1940’s, and its molecular structure and the principles of coding genetic information were established in the 1950’s and 1960’s.

The concept of the gene became more profound and more precise as the study of genetics at the subcellular and molecular level continued. In experiments on the inheritance of different traits the gene was postulated as the elementary, indivisible unit of heredity and was regarded in the light of cytological data as a separate part of the chromosome. At the molecular level, the gene was considered an integral part of the DNA molecule, capable of replication and possessing a specific structure in which the program for the development of one or more traits was coded. In the 1950’s, the American geneticist S. Benzer showed that in microorganisms every gene consists of several different parts capable of mutating and crossing over. This confirmed the idea developed in the 1930’s by A. S. Serebrovskii and N. P. Dubinin, who concluded from genetic analysis that the gene has a complex structure.

In 1967–69, viral DNA was synthesized in vitro and the gene of yeast alanine transport RNA was chemically synthesized. The heredity of somatic cells in vivo and in tissue culture became a new field of research. Scientists discovered that it is possible to hybridize experimentally the somatic cells of different species. The phenomena of heredity became key factors in many practical questions and in understanding certain biological processes.

The role of heredity in evolution was clear to Darwin. The establishment of the discrete character of heredity removed one of the important objections to Darwinism: the crossing of individuals in whom hereditary changes have appeared must “dilute” these changes or weaken their expression. According to Mendel’s laws, however, the changes are not destroyed or blended but reappear in the offspring under certain conditions. In populations the phenomena of heredity appeared to be complex processes based on crosses of individuals, as well as on selection, mutations, and genetic-automatic processes. The first to point this out was S. S. Chetverikov (1926), who demonstrated experimentally the accumulation of mutations within a population. I. I. Shmal’gauzen (1946) hypothesized that a “mobilization reserve of hereditary mutation” was the material for the creative activity of natural selection under changing environmental conditions. The significance of different types of mutations in evolution was demonstrated.

Evolution is defined as gradual and repeated change in the heredity of a species. At the same time, heredity, which ensures the continuity of species organization, is a fundamental property of life that has evolved over a long period of time and that is related to the physicochemical structure of the elementary units of the cell, particularly its chromosomal apparatus. The principles of the organization of this physicochemical structure (the genetic code) appear to be universal for all living things and are regarded as the most important attribute of life.

Ontogeny, which starts with fertilization of the egg and proceeds under concrete environmental conditions, is also controlled by heredity. Thus, the set of genes that the organism receives from its parents (the genotype) differs from the complex of the organism’s traits at various stages of its development (the phenotype). The role of the genotype and the environment in the formation of the phenotype may differ. But it is essential to bear in mind that the organism’s normal reaction to environmental influences is genotypically determined. Because changes in the phenotype are not adequately reflected in the genotypic structure of the sex cells, the traditional view of the inheritance of acquired characteristics has been rejected for having no factual basis and for being theoretically unsound. The mechanism by which heredity is realized in the development of an individual seems to be related to the successive action of different genes. Heredity depends on the interaction of the nucleus and cytoplasm, in which various proteins are synthesized in accordance with a program coded in DNA and transmitted to the cytoplasm by messenger RNA.

The laws of heredity are very important in agriculture and medicine. They are the basis for developing new plant varieties and animal breeds and for improving existing ones. The study of the laws of heredity led to the scientific substantiation of already known empirical breeding methods and resulted in the development of new methods (experimental mutagenesis, heterosis, and polyploidy, for example). Discoveries in human genetics showed that the genes responsible for the development of various anomalies and hereditary metabolic, mental, and other diseases are fairly common. Genetic counseling is designed to help reduce the probability of the birth of children with hereditary diseases. Early diagnosis permits the prompt institution of the required therapy. Heredity is an important factor in the reactions of people to drugs and other chemical substances and in human immunological responses. There is no question that molecular genetic mechanisms play a role in the etiology of malignant tumors.

The phenomena of heredity appear in different forms, depending on the level of life at which they are studied (molecule, cell, organism, or population). Ultimately, however, heredity is maintained by the replication of the material units of heredity (genes and cytoplasmic elements) whose molecular structure is known. The regular, matric character of their replication may be disturbed by mutations of particular genes or by reconstructions of the genetic systems as a whole. Any change in a replicating element is invariably inherited.

REFERENCES

Wilson, E. Kletka i ee rol’ ν razvitii i nasledstvennosti, vols. 1–2. Moscow-Leningrad, 1936–40. (Translated from English.)
Morgan, T. Izbrannye raboty po genetike. Moscow-Leningrad, 1937. (Translated from English.)
Sager, R. , and F. Ryan. Tsitologicheskie i khimicheskie osnovy nasledstvennosti. Moscow, 1964. (Translated from English.)
Stahl, F’. Mekhanizmy nasledstvennosti. Moscow, 1966. (Translated from English.)
Lobashev, M. E. Genetika, 2nd ed. Leningrad, 1967.
Gaisinovich, A. E. Zarozhdenie genetiki. Moscow, 1967.
Watson, J. D. Molekuliarnaia biologiia gena. Moscow, 1967. (Translated from English.)
Uspekhi sovremennoigenetiki (collection of articles), fases. 1–4. Moscow, 1967–72.
Klassiki sovetskoi genetiki (collection of articles). Leningrad, 1968.
Dubinin, N. P. Obshchaia genetika. Moscow, 1970.
Yeas, M. Biologicheskii kod. Moscow, 1971. (Translated from English.)
Mettler, L. , and T. Gregg. Genetika populiatsii i evoliutsiia. Moscow, 1972. (Translated from English.)
Weber, E. Mathematische Grundlagen der Genetik. Jena, 1967.
Sinnott, E. , L. Dunn, and T. Dobzhansky. Principles of Genetics. New York, 1958.

P. F. ROKITSKII

heredity

[hə′red·əd·ē] (genetics) The transmission of phenotypes and alleles from one generation to the next. The sum of genetic endowment obtained from the parents.

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

heredity

[hĕ-red´ĭ-te] the genetic transmission of traits from parents to offspring. The hereditary material is contained in the ovum (oocyte) and sperm, so that the child's heredity is determined at the moment of conception.Chromosomes and Genes. Inside the nucleus of each germ cell are structures called chromosomes, composed of deoxyribonucleic acid (DNA) on a framework of protein. genes are segments of the DNA molecule; there are thousands of them in each cell, each carrying a specific hereditary trait, which may be physical, biochemical, or physiologic. Thus genes affect not only the physical appearance of an individual but also the physiologic makeup, the tendency to develop certain diseases, and the daily activities of all the cells of the body.
The human ovum and the human sperm each contain 23 chromosomes. Aside from the pair determining the sex, each chromosome in the sperm is similar in shape and size to one in the ovum. When the sperm penetrates the ovum, the fertilized ovum thus contains 23 pairs of chromosomes, or 46 chromosomes in all. The fertilized ovum (zygote) then begins to reproduce itself by dividing (mitosis). The original cell divides and forms two cells, each of these divides and forms a total of four cells, and so on until a many-celled embryo begins to take form. In the process of cell division, the chromosomes in the nucleus have the ability to make duplicates of themselves. They do not split in two, but instead each one produces another chromosome exactly like itself. When the two cells are formed from one, the chromosomes are divided so that each cell contains the same number and kind of chromosomes as the original. For this reason, all the cells in the developing embryo and in the human body, except the ovum and sperm, contain identical sets of 46 chromosomes.
The ovum and the sperm are formed by a special process of cell division (meiosis) in which each sperm or ovum receives only one member of each chromosome pair. If this were not true, and sperm or ova contained the full complement of 46 chromosomes, the cells of the offspring would have 92 chromosomes, their offspring would have 184, and so on. As it is, the amount of hereditary material in the body cells remains constant from generation to generation.
In the formation of the germ cells, it is a matter of chance which member of each pair of chromosomes goes to a given ovum or sperm. It is also purely a matter of chance which sperm fertilizes an ovum. All in all,, there are about 70 trillion possible combinations of chromosomes that a child could inherit.Inherited Traits. Although many details of human heredity are not known, we know that the child receives a set of genes from the parents. These genes (hereditary determinants) develop into characteristics reflecting those of the parents, grandparents, and other ancestors. Before birth these inherited traits are influenced by conditions within the mother's body; after birth they can be shaped by environmental influences such as diet, training, and education.
Some specific aspects of human heredity are well understood. One member of a chromosome pair is contributed by one parent and the other by the other parent. A gene in one chromosome acts on the same trait as a gene in the same position on the other chromosome. It has been found that one gene may be more powerful in its influence than the other gene that acts on the same trait. The more powerful gene is called a gene" >dominant gene and the other is called a gene" >recessive gene.Sex-Linked Traits. Certain hereditary traits are known as sex-linked because they are carried on the X chromosome. Color blindness is an example. This condition, in which colors appear as varying shades of gray, is rare in females but appears in about 8 per cent of the male population. The genes for color vision are located on the X chromosomes, and the gene for normal vision is dominant to that for color blindness. A female having one gene for normal vision on one X chromosome and one for color blindness on the other will have normal vision, since the color blindness gene is recessive. A male, however, having only one X chromosome, will be color blind if that chromosome has the recessive gene, since there is no corresponding dominant gene to suppress it. It is possible for a female to be color blind, if she has two of the recessive genes, but it is quite rare that these two genes come together in one person.
Another characteristic associated with sex is baldness. The gene for baldness is dominant in males and recessive in females. Thus a male need have only one gene for baldness for the trait to be expressed, but a female must have two.Hereditary Diseases. These should be distinguished from congenital birth defects. A congenital defect is one that the infant is born with, such as a cleft lip, a birthmark, or congenital syphilis, but the defect can arise during conception or pregnancy and not be related to heredity. Hereditary diseases, on the other hand, are passed from generation to generation by genes. Some diseases, such as cystic fibrosis, are transmitted by recessive genes.Role of Mutation. Mutation is the term used for a spontaneous change in a chromosome or gene. Normally chromosomes duplicate themselves exactly during cell division. Occasionally, however, the new cells contain an altered gene or chromosome. If the mutation occurs in an ovum or sperm involved in reproduction, the new trait will be expressed in the offspring.
Many mutations are so minor that they have no visible effect. A mutation that is very harmful will usually result in the death of the fetus and spontaneous abortion. Occasionally a mutation is beneficial. Favorable mutations gradually tend to spread through a population. The accumulation of mutations over millions of years has contributed to evolution.

he·red·i·ty

(hĕ-red'i-tē), 1. The transmission of characters from parent to offspring by information encoded in the parental germ cells. 2. Genealogy. [L. hereditas, inheritance, fr. heres (hered-), heir]

heredity

(hə-rĕd′ĭ-tē)n. pl. heredi·ties 1. The genetic transmission of characteristics from parent to offspring.2. The sum of characteristics and associated potentialities transmitted genetically to an individual organism.

heredity

The transmission of characteristics from one generation to the next. See Progeny. Cf Congenital.

he·red·i·ty

(hĕr-ed'i-tē) 1. The transmission of characteristics from parent to offspring by information encoded in the parental germ cells. 2. Genealogy. [L. hereditas, inheritance, fr. heres (hered-), heir]

heredity

The transmission from parent to child of any of the characteristics coded for in the molecular sequences on DNA known as the GENES. Heredity is mediated by way of the CHROMOSOMES which, essentially, consist of DNA. Of the 46 chromosomes in each body cell, 23 come from the mother and 23 from the father. The pattern of genes on the chromosomes is called the genotype; the resulting physical structure with all its characteristics is called the phenotype.

heredity

the transmission of characteristics from one generation to another via a mechanism involving GENES and CHROMOSOMES.

he·red·i·ty

(hĕr-ed'i-tē) Transmission of characters from parent to offspring by information encoded in the parental germ cells. [L. hereditas, inheritance, fr. heres (hered-), heir]

Patient discussion about heredity

Q. What pattern of heredity does diabetes follow? I know that baldness comes from your mother's father. How does diabetes travel through generations?A. Ninety percent of children who develop type 1 diabetes actually have no relative with the disease. But it’s an auto immune disease. That means that some people are in risk of getting diabetes type 1. Depends on the immune system they inherited. It’s not “recessive” or “dominant”, if your parent has type 1 – you have a 25% chance of getting the risk factor.

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Synonyms for heredity

noun genetics

Synonyms

Synonyms for heredity

noun the biological process whereby genetic factors are transmitted from one generation to the next

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noun the total of inherited attributes

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