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gene family 291 genetic knockout
encoding a protein that is responsible for either antigenicity
or drug susceptibility, respectively.
gene family
Genes that encode proteins with similar structures and
frequently with similar functions.
gene gun
An apparatus that forces tiny plasmid-coated gold particles
into the cytoplasm of living cells, which synthesize the
antigen encoded by the plasmid. Used for experimental
vaccination.
gene knockout
Gene disruption by homologous recombination. It may refer
to a cell or animal in which the function of a specific gene
is purposely eliminated by replacing the normal gene with
an inactive mutant gene.
gene mapping
Gene localization or gene order. Gene localization can be in
relationship to other genes or to a chromosomal band. The
term may also refer to the ordering of gene segments.
gene rearrangement
Genetic shuffling that results in elimination of introns and
the joining of exons to produce mRNA. Gene rearrangement
within a lymphocyte signifies its dedication to the
formation of a single cell type via immunoglobulin synthesis
by B lymphocytes or production of a β chain receptor by
T lymphocytes. Neoplastic transformation of lymphocytes
may be followed by the expansion of a single clone of cells
detectable by Southern blotting.
gene segments
Multiple short DNA sequences in immunoglobulin and
T cell receptor genes that can undergo rearrangements
in many combinations to yield a vast diversity of immunoglobin
or T cell receptor polypeptide chains. A gene
segment is a short, germline sequence of DNA derived
from the variable (V) diversity (D) or joining (J) families.
It combines randomly by way of V(D)J recombination with
one or two other gene segments to form a V exon in either
Ig or TCR loci. Gene segments do not possess RNA splice
donor and acceptor sites.
gene therapy
The introduction of a normal functional gene into cells of the
bone marrow to correct a genetic defect. Also termed somatic
L 1
V 1
L 1
= Promoter
L 2
V 1
L = Leader sequence
V = Variable region
D = Diversity regions
J = Junction regions
V 2
C = Constant region coding block
E = Enhancer sequence
L n
V n
L n
gene therapy because it does not affect germline genes. A
mechanism to achieve a therapeutic effect by transferring
new genetic information into affected cells or tissues or into
accessory cells. Adenosine deaminase deficiency has been successfully
treated by this method. The technique also applies to
patients with neoplasms or degenerative syndrome.
generalized anaphylaxis
The signs and symptoms of anaphylactic shock manifest
within seconds to minutes following the administration
of an antigen or allergen that interacts with specific
immunoglobulin E (IgE) antibodies bound to mast cell or
basophil surfaces, causing the release of pharmacologically
active mediators that include vasoactive amines from their
granules. Symptoms may vary from transient respiratory
difficulties (due to contraction of the smooth muscle and
terminal bronchioles) to even death.
generalized vaccinia
A condition observed in some children vaccinated against
smallpox with vaccinia virus. Numerous vaccinia skin
lesions occurred in children who had primary immunodeficiencies
in antibody synthesis. Although usually selflimited,
children who also had atopic dermatitis in addition
to the generalized vaccinia often died.
generative lymphoid organ
An organ in which lymphocytes arise from immature precursor
cells. The principal generative lymphoid organ for T
cells is the thymus, and for B cells it is bone marrow.
genetic code
The codons (nucleotide triplets) correlating with amino
acid residues in protein synthesis. The nucleotide linear
sequence in mRNA is translated into the amino acid residue
sequence.
genetic immunization
The inoculation of plasmid DNA encoding a protein into
muscle for the purpose of inducing an adaptive immune
response. For reasons yet to be explained, the plasmid DNA
is expressed and induces T cell responses and antibody
formation to the protein that the DNA encoded.
genetic knockout
A technique to introduce precise genetic lesions into the
mouse genome to cause gene disruption and generate an
animal model with a specific genetic defect. Specific defects
V n
D 1
D n
J
D n
Immunoglobulin gene rearrangement.
E
J
C µ
E
C µ
Germ line DNA
configuration
Rearrangement
B Cell DNA
G