General genetics

GENERAL GENETICS : the study of genes and their heredity.

Table of contents :

Reproduction

Heredity and variability

Population genetics

Taxonomy of living organisms

Conservation genetics and ecology

Paleoanthropology

Web resources

Bibliography

bacterial genetics : the study of mechanisms of heredity in bacteria.
biochemical genetics : the science concerned with the chemical and physical nature of genes and the mechanism by which they control the development and maintenance of the organism.
mathematical genetics : the statistical analysis of probabilities of genetic transmission, genes in populations, and hypothesis testing.
molecular genetics : that branch of genetics concerned with the molecular structure and activities of the genetic material, including the replication of DNA, its transcription into RNA, and the translation of RNA to form proteins.

gene : a segment of a DNA molecule that contains all the information required for synthesis of a product (polypeptide chain or RNA molecule), including both coding and noncoding sequences. It is the biologic unit of heredity, self-reproducing, and transmitted from parent to progeny. Each gene has a specific position (locus) on the chromosome map.

allelic genes / alleles : any alternative form of a gene that can occupy a particular chromosomal locus. In humans and other diploid organisms there are two alleles, one on each chromosome of a homologous pair

multiple alleles : a series of > 2 alleles.
Mendel's laws : the laws of inheritance of single-gene traits that form the basis of the science of genetics, first described by Gregor Mendel in 1865. From experimental crosses of pea plants differing in one or more characteristics determined by single genes, and counting the types of progeny in successive generations, Mendel derived 2 laws now usually expressed as

the law of segregation (the members of a pair of allelic genes segregate from one another and pass to different gametes)
the law of independent assortment (genes that are not alleles are distributed to the gametes independently of one another).

autosomal gene : a gene located on any chromosome that is not a sex chromosome
sex-conditioned or -influenced gene : a gene that is fully expressed in one sex only, e.g. human baldness.
sex-limited gene : a sex-linked or autosomal gene that will produce an effect in one sex only.
sex-linked gene : a gene carried on a sex chromosome (X or Y); only X linkage has clinical significance, and sex linkage is more correctly called X linkage.

X-linked gene : a gene carried on the X chromosome; the corresponding trait, whether dominant or recessive, is always expressed in males, who have only one X chromosome. X linkage is used sometimes synonymously with sex linkage since no genetic disorders have as yet been associated with genes on the Y chromosome.
Y-linked gene : a gene located on the Y chromosome; the trait determined by it is therefore exhibited only by males and is transmitted by a father to all of his sons. Other than the genes that determine maleness, no clinically significant Y-linked genes have been identified in human beings.

holandric genes : genes in the nonhomologous region of the Y chromosome.

chimeric gene : an artificial gene constructed by juxtaposition of fragments of unrelated genes or other DNA, which may themselves have been altered in sequence.
penetrance : the frequency of expression of a genotype. If it is < 100%, the trait is said to exhibit reduced penetrance or lack of penetrance. In an individual who has a genotype that characteristically produces an abnormal phenotype but is phenotypically normal, the trait is said to be nonpenetrant.
dominant gene : one that is phenotypically expressed when present either in homozygous or heterozygous form
recessive gene : one that is phenotypically expressed only when homozygous or hemizygous
codominant genes / codominance : alleles that are both fully expressed in the heterozygote
complementary or reciprocal genes : 2 independent pairs of nonallelic genes, neither of which will produce its effect in the absence of the other
gene complex : a DNA segment containing a number of genes coding for products with related functions, e.g. the human major histocompatibility complex (MHC).
cumulative genes / polygenes : one of a group of nonallelic genes (multiple factors or cumulative genes) that interact to influence the same character in the same way so that the effect is cumulative
histocompatibility (H) gene : a gene that determines a histocompatibility antigen.
housekeeping gene : a gene that theoretically must be expressed in all cells because it encodes proteins needed for basic functioning.
immune response (Ir) genes : genes that govern the immune response to certain antigens. Animals carrying the gene are responders; those lacking the gene are nonresponders. In all species studied they are autosomal dominant genes that map with the genes for class II MHC antigens; thus the HLA-D/DR genes are probably immune response genes in humans.
immune suppressor (Is) genes : genes governing the ability of suppressor T cells to respond to certain antigens.
immunoglobulin genes : the genes coding for immunoglobulin heavy and light chains, which are organized in three loci coding for k light chains, l light chains, and heavy chains found on human chromosomes 2, 22, and 14, respectively. These genes undergo several DNA rearrangements during the differentiation of stem cells into B cells and plasma cells, permitting synthesis of the various immunoglobulin classes.
cell interaction (CI) genes : genes of the major histocompatibility complex that control cell-cell interactions between B cells, T cells, and macrophages and between cytotoxic T cells and target cells.
lethal gene : a gene the presence of which brings about the death of the organism, or permits its survival only under certain conditions; see also lethal equivalent.
sublethal gene : a gene the presence of which handicaps or impairs the function of the organism.
major gene : a gene whose effect on the phenotype is always evident, regardless of how this effect is modified by other genes.
mutant gene : a gene in which the loss, gain, or exchange of material has resulted in a permanent transmissible change in function. Such a gene may have become practically inactive (amorph), may act to antagonize or inhibit normal activity (antimorph), may act to increase normal activity (hypermorph), or may show only a slight reduction in its effectiveness (leaky gene or hypomorph)

silent gene or allele : a mutant gene having no detectable phenotypic effect.
leaky gene : one in which a switch in the sequence of bases in a nucleotide results in the production of a mutant protein that, because of a single amino acid replacement, has only partial enzymatic activity; a hypomorph.

wild-type gene : the normal allele of a gene, sometimes symbolized by ⁺.

wild type : in genetics, the standard phenotype for any experimental organism; also a gene that determines a standard phenotypic trait

pleiotropic gene : one producing many effects in the phenotype.
repressed gene : one that under normal conditions does not always function to produce the maximum number of enzymes
derepressed gene : one that in response to an environmental demand for a particular enzyme functions to increase production of that enzyme
split gene : a gene containing multiple exons and at least one intron.
supplementary genes : 2 independent pairs of genes that interact in such a way that one dominant will produce its effect even in the absence of the other, but the second requires the presence of the first to be effective.
syntenic genes : genes located on the same chromosome.
tumor suppressor gene / antioncogene : a gene whose function is to limit cell proliferation and loss of whose function leads to cell transformation and tumor growth

structural gene : a gene that specifies the amino acid sequence of a polypeptide chain. Messenger RNA is its primary product.
operator gene or locus : in bacterial genetics, a gene that serves as a starting point for reading the genetic code and controls the activity of the structured genes by interacting with a repressor
regulator, regulatory or repressor gene : in genetic theory, a gene that synthesizes repressor, a substance which, through interaction with the operator gene, switches off the activity of the structural genes associated with it in the operon. More generally, a gene whose product affects the activity of other genes.

haplotype : the combination of alleles or genetic markers that is found on a single chromosome of a given individual.
Galton 's law : each parent contributes, on an average, one half, or (0.5), of an individual's heritage, each grandparent one fourth, or (0.5)², each greatgrandparent one eighth, or (0.5)³, etc.
Galton 's law of regression : average parents tend to produce average children, but the offspring of extreme parents inherit the parental peculiarities in a less marked degree than the latter were manifested in the parents themselves
complementation : the interaction between 2 sets of cellular or viral genes introduced into the same cell, such that the cell can function even though each set of genes carries a mutated, nonfunctional gene; it indicates that the defects are not identical.

intercistronic or intergenic complementation : the essentially full restoration of wild-type function in a cis-trans test when two mutations are located in two different cistrons (genes)
intracistronic, interallelic or intragenic complementation : the partial restoration of function sometimes seen in the cis-trans test when the two mutations are located at different sites within the same cistron.

eugenics / orthogenics : the improvement of a population by selection of its best specimens for breeding

negative eugenics : that concerned with prevention of reproduction (procreation) by individuals possessing inferior or undesirable traits.
positive eugenics : that concerned with promotion of optimal reproduction of individuals possessing superior or desirable traits.

dysgenics : the study of racial deterioration
backcross : in experimental genetics, a mating between a heterozygote and a homozygote.

double backcross : the mating between a double heterozygote and a homozygote.

Web resources

The Virtual Library - Genetics
Free Association, Nature Genetics blog
Genetic science learning centre (GSLC) at the University of Utah
DNA from the beginning at Cold Spring Harbor Laboratory
Mendelweb : origins of classical genetics
Molecular genetics at Oklahoma State University
Genomics glossary by Cambridge Healthtech Institute (CHI)
Genetic vocabulary at Mahasarakham University, Thailand
Genetics glossary by Birgid Schlindwein
Moleculare Genetik by Stefan Dübel
Full-text of original papers on genomics
dmoz Open Directory Project (ODP) : Genetics
Usenet bionet.molbio.gene-org
Virtual Genetics Lab (VGL) software for Macs®, Linux, UNIX®, and Windows. Created by a team of graduate students at the UMASS Boston, VGL allows students to perform in silico crossings of imaginary flies and, by observing the characteristics of the progeny, predict the genetic makeup of the parents, show how theoretical phenotypes are being passed on, and determine complex traits, such as incomplete dominance and others.
resources for genetics in primary care ;

patient support/patient advocacy organisations :

health professional organisations involved in genetic education :

Genetic condition specific information :

GeneClinics an electronic clinical genetics knowledge base
GeneTests an electronic database of testing laboritores and education

Government groups/foundations :

Bibliography

Griffiths, Anthony J.F.; Gelbart, William M.; Miller, Jeffrey H.; Lewontin, Richard C.: Introduction To Genetic Analysis, 7^th ed., New York: W H Freeman & Co; ©1999 [free at NCBI BookShelf !]
Griffiths, Anthony J.F.; Gelbart, William M.; Miller, Jeffrey H.; Lewontin, Richard C. : Modern Genetic Analysis, New York: W H Freeman & Co; ©1999 [free at NCBI BookShelf !]

Genomes

[free at NCBI BookShelf !]

Strachan, Tom and Read, Andrew P. : Human Molecular Genetics 2. 2nd ed., Oxford, UK: BIOS Scientific Publishers Ltd; 1999 [free at NCBI BookShelf !]
Sequence - Evolution - Function Computational Approaches in Comparative Genomics. Koonin, Eugene V. and Galperin, Michael Y. Norwell (MA): Kluwer Academic Publishers; 2003 [free at NCBI BookShelf !]

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