Dominant gene


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gene

 [jēn]
one of the biologic units of heredity, self-reproducing, and located at a definite position (locus) on a particular chromosome. Genes make up segments of the complex deoxyribonucleic acid (DNA) molecule that controls cellular reproduction and function. There are thousands of genes in the chromosomes of each cell nucleus; they play an important role in heredity because they control the individual physical, biochemical, and physiologic traits inherited by offspring from their parents. Through the genetic code of DNA they also control the day-to-day functions and reproduction of all cells in the body. For example, the genes control the synthesis of structural proteins and also the enzymes that regulate various chemical reactions that take place in a cell.

The gene is capable of replication. When a cell multiplies by mitosis each daughter cell carries a set of genes that is an exact replica of that of the parent cell. This characteristic of replication explains how genes can carry hereditary traits through successive generations without change.
allelic gene allele.
complementary g's two independent pairs of nonallelic genes, neither of which will produce its effect in the absence of the other.
DCC gene (deleted in colorectal carcinoma) a gene normally expressed in the mucosa of the colon but reduced or absent in a small proportion of patients with colorectal cancer.
dominant gene one that produces an effect (the phenotype) in the organism regardless of the state of the corresponding allele. An example of a trait determined by a dominant gene is brown eye color. See also heredity.
histocompatibility gene one that determines the specificity of tissue antigenicity (hla antigens) and thus the compatibility of donor and recipient in tissue transplantation and blood transfusion.
holandric g's genes located on the Y chromosome and appearing only in male offspring.
immune response (Ir) g's genes of the major histocompatibility complex that govern the immune response to individual immunogens.
immune suppressor (Is) g's genes that govern the formation of suppressor T lymphocytes.
immunoglobulin g's the genes coding for immunoglobulin heavy and light chains, which are organized in three loci coding for κ light chains, λ light chains, and heavy chains.
K-ras gene a type of oncogene.
lethal gene one whose presence brings about the death of the organism or permits survival only under certain conditions.
major gene a gene whose effect on the phenotype is always evident, regardless of how this effect is modified by other genes.
mutant gene one that has undergone a detectable mutation.
operator gene one serving as a starting point for reading the genetic code, and which, through interaction with a repressor, controls the activity of structural genes associated with it in the operon.
gene pool all of the genes possessed by all of the members of a population that will reproduce.
recessive gene one that produces an effect in the organism only when it is transmitted by both parents, i.e., only when the individual is homozygous. See also heredity.
regulator gene (repressor gene) one 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.
sex-linked gene a gene carried on a sex chromosome (X or Y); only X linkage has clinical significance. See X-linked gene.
structural gene one that forms templates for messenger RNA and is thereby responsible for the amino acid sequence of specific polypeptides.
tumor suppressor gene a gene whose function is to limit cell proliferation and loss of whose function leads to cell transformation and tumor growth; called also antioncogene.
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. the term “X-linked” is sometimes used synonymously with “sex-linked,” since no genetic disorders have as yet been associated with genes on the Y chromosome.

dom·i·nance of traits

an expression of the apparent physiologic relationship existing between two or more genes that may occupy the same chromosomal locus (alleles). At a specific locus there are three possible combinations of two allelic genes, A and a: two homozygous (AA and aa) and one heterozygous (Aa). If a heterozygous individual presents only the hereditary characteristic determined by gene A, but not a, A is said to be dominant and a recessive; in this case, AA and Aa, although genotypically distinct, should be phenotypically indistinguishable. If AA, Aa, and aa are distinguishable, each from the others, A and a are codominant.

dom·i·nance of traits

(dom'i-năns trāts)
An expression of the apparent physiologic relationship existing between two or more genes that may occupy the same chromosomal locus (alleles). At a specific locus there are three possible combinations of two allelic genes, A and a: two homozygous (AA and aa) and one heterozygous (Aa). If a heterozygous individual presents only the hereditary characteristic determined by gene A, but not a, A is said to be dominant and a recessive; in this case, AA and Aa, although genotypically distinct, should be phenotypically indistinguishable. If AA, Aa, and aa are distinguishable, each from the others, A and a are codominant.

gene

(jen) [Ger. Gen, ult. fr Gr. genos, kind, race, descent]
Enlarge picture
AUTOSOMAL DOMINANT INHERITANCE
Enlarge picture
AUTOSOMAL DOMINANT INHERITANCE
The basic unit of heredity, made of DNA, the code for a specific protein. Each gene occupies a certain location on a chromosome. Genes are self-replicating sequences of DNA nucleotides, subject to random structural changes (mutations). Hereditary traits are controlled by pairs of genes in the same position on a pair of chromosomes. These alleles may be either dominant or recessive. When both pairs of an allele are either dominant or recessive, the individual is said to be homozygous for the traits coded by the gene. If the alleles differ (one dominant and one recessive), the individual is heterozygous. See: illustration; chromosome; DNA; RNA

autosomal dominant gene

A dominant gene that is found on any chromosome other than the X or Y chromosome.

autosomal recessive gene

A recessive gene that is found on any chromosome other than the X or Y chromosome.

BRCA1 gene

A breast cancer gene found in a small percentage of patients with this malignancy, and carried by some individuals who will develop breast cancer later in life.

Patient care

BRCA1 Gene Mutation: Patient care focuses on determining the family history of the patient and referral to a genetic counselor with expertise in this mutation when appropriate.

BRCA2 gene

A breast cancer gene found in a small number of patients with breast and ovarian cancers, and carried by some individuals who will develop breast cancer later in life.

complementary genes

Nonallelic, independently located genes, neither of which will be expressed in the absence of the other.

cystic fibrosis transmembrane conductance regulator gene

The gene that codes for a protein that regulates the movement of ions, esp. chloride, across cell membranes.

dominant gene

See: dominant

histocompatibility gene

One of the genes composing the HLA complex that determines the histocompatibility antigenic markers on all nucleated cells. These genes create the antigens by which the immune system recognizes “self” and determines the “nonself” nature of pathogens and other foreign antigens. These antigens are crucial determinants of the success or failure of organ transplantation.
See: histocompatibility locus antigen

holandric gene

A gene located in the nonhomologous portion of the Y chromosome of males.

homeobox gene

Any transcription factor that regulates the growth, differentiation, replication, and movement of cells in the body. These genes influence both normal and abnormal embyological development and the development or suppression of malignant tumors.

housekeeping gene

A gene expressed in nearly every cell and every tissue of an organism, i.e., one that encodes a protein fundamental to cellular activity throughout the organism.

immune response gene

One of the many genes that control the ability of leukocytes to respond to specific antigens.
See: antigen; B cell; HLA complex; T cell

inhibiting gene

A gene that prevents the expression of another gene.

interleukin-28B gene

A genetic variant that increases the likelihood of having a favorable to response to antiviral treatment for chronic hepatitis C, genotype 1 infection (traditionally the most resistant hepatitis C genotype).

lethal gene

A gene that creates a condition incompatible with life and usually results in the death of the fetus.

modifying gene

A gene that influences or alters the expression of other genes.

mutant gene

An altered gene that permanently functions differently than it did before its alteration.

operator gene

A gene that controls the expression of other genes.
See: operon

gene p53

A gene thought to be important in controlling the cell cycle, DNA repair and synthesis, and programmed cell death (apoptosis). Mutations of p53 have occurred in almost half of all types of cancer, arising from a variety of tissues. Mutant types may promote cancer. The normal, wild-type gene produces a protein important in tumor suppression.

pleiotropic gene

A gene that has multiple effects.

posttranscriptional gene silencing

RNA interference.

presenilin gene

Rare traits responsible for early-onset Alzheimer's disease.

RB gene

Tumor suppressor gene encoding for the retinoblastoma (RB) protein, mutations of which are associated with various human tumors, including retinoblastoma, osteosarcoma, some leukemias, and some adenocarcinomas.
See: tumor suppressor gene; retinoblastoma

recessive gene

A trait that is not expressed unless it is present in the genes received from both parents. A recessive trait may be apparent in the phenotype only if both alleles are recessive.
Synonym: recessive characteristic

regulator gene

A gene that can control some specific activity of another gene.

sex-linked gene

Sex-linked characteristic.

structural gene

A gene that determines the structure of polypeptide chains by controlling the sequence of amino acids.

susceptibility gene

A gene that increases a person's likelihood of contracting a heritable illness.

tumor suppressor gene

A gene that suppresses the growth of malignant cells.
See: cancer

X-linked gene

A gene on the X chromosome for which there is no corresponding gene on the Y chromosome. X-linked genes (e.g., the gene for red-green color blindness) are expressed but in males even these genes are recessive because there is no correponding gene to dominate them.

Dominant gene

A gene, whose presence as a single copy, controls the expression of a trait.
Mentioned in: Genetic Testing
References in periodicals archive ?
The presence of positive and significant values of d (additive) and h (dominance) in these two crosses, disclosed the involvement of both additive and dominant gene actions in the inheritance of ear height.
These include a dominant gene on chromosome 1B in winter wheat cultivar Atlas 66 (Kleijer et al., 1977) and a dominant gene in an Aegilops tauschii Coss.
Co-presence of both additive and dominant gene action in the control of this character was envisaged by the significance of both D and H (H1 H2) components of genetic variation.
A goodness-of-fit to a 3:1 ratio ([chi square] = 0.01 and P = 0.91) of number of resistant to susceptible [F.sub.2] plants to race 51 was observed, it was hypothesized that a single dominant gene controlled SR to race 51.
The results showed that different genotypes and cross combinations have dominant gene for different traits.
Two genotypes (CPI84495 and YSED18) are also yellow-seeded but the seed color is governed by a dominant gene (Green and Dribnenki, 1995).
To test the genetic hypothesis of a single dominant gene controlling rust resistance, the chi-square test was used to test goodness-of-fit to a 3:1 resistant to susceptible ratio in the [F.sub.2] generation or a 1:2:1 segregation of nonsegregating for rust resistance, segregating, and nonsegregating for rust susceptibility in the [F.sub.3] generation.
This ratio corresponds to a model involving a single dominant gene, for which the dominant homozygote and/or the heterozygote exhibit variable expression, sometimes resulting in fully naked plants and sometimes resulting in mosaic plants.
The progeny of each generation segregated for short and long cooking times in a ratio approaching 3:1 (Table 3), which corresponds to a two dominant gene model.
This ratio is consistent with the single dominant gene control of vigor restoration previously reported (Jan, 1992).
In some genetic backgrounds, resistance in U00297 is conferred by a single dominant gene, which is independent of resistance genes found in cultivars AND277 and G5686, while in others, resistance is due to epistatic gene interaction involving two or three genes.