Untitled - D Ank Unlimited

DNA library 233 doctrine of original antigenic sin
generate uniformly nicked genomic DNA during apoptosis.
Following gel electrophoresis, DNA fragments migrate in a
pattern resembling a ladder, with individual bands differing
by approximately 200 base pairs.
DNA library
A gene library or clone library comprised of multiple nucleotide
sequences that are representative of all sections of the
DNA in a particular genome. It is a random assemblage of
DNA fragments from one organism, linked to vectors and
cloned in an appropriate host. This prevents any individual
sequence from being systematically excluded. Adjacent
clones will overlap, and cloning large fragments helps to
ensure that the library will contain all sequences. The DNA
to be investigated is reduced to fragments by enzymatic
or mechanical treatment, and the fragments are linked to
appropriate vectors such as plasmids or viruses. The altered
vectors are then introduced into host cells. This is followed
by cloning. Transcribed DNA fragments (exons) and
nontranscribed DNA fragments (introns or spacers) are part
of the gene library. A probe may be used to screen a gene
library to locate specific DNA sequences.
DNA ligase
An enzyme that joins DNA strands during repair and
replication. It serves as a catalyst in phosphodiester, binding
between the 3′-OH and the 5′-PO 4 of the phosphate backbone
of DNA.
DNA microarray
A technique in which a different DNA is placed on a small
section of a microchip. The microarray is then used to
evaluate expression of RNA in normal or neoplastic cells.
DNA nucleotidylexotransferase (terminal deoxynucleotidyl
transferase [TdT])
DNA polymerase that randomly catalyzes deoxynucleotide
addition to the 3′-OH end of a DNA strand in the absence
of a template. It can also be employed to add homopolymer
tails. Immature T and B lymphocytes contain TdT. The
thymus is rich in TdT, which is also present in the bone
marrow. TdT inserts a few nucleotides in T cell receptor and
immunoglobulin gene segments at the V–D, D–J, and V–J
junctions. This enhances sequence diversity.
DNA polymerase
An enzyme that catalyzes DNA synthesis from deoxyribonucleotide
triphosphate by employing a template of
either single- or double-stranded DNA. This is known as
DNA-dependent (direct) DNA polymerase, in contrast to
RNA-dependent (direct) DNA polymerase, which employs
an RNA template for DNA synthesis.
DNA polymerase I
DNA-dependent DNA polymerase whose principal function
is in DNA repair and synthesis. It catalyzes DNA synthesis
in the 5′ to 3′ sense. It also has a proofreading function
(3′ → 5′ exonuclease) and a 5′ → 3′ exonuclease.
DNA polymerase II
DNA-dependent DNA polymerase in prokaryotes. It
catalyzes DNA synthesis in the 5′ to 3′ sense, has a
proofreading function (3′ → 5′ exonuclease), and is thought
to play a role in DNA repair.
DNA polymerase III
DNA-dependent DNA polymerase in prokaryotes that catalyzes
DNA synthesis in the 5′ to 3′ sense. It is the principal
synthetic enzyme in DNA replication. It has a proofreading
function (3′ → 5′ exonuclease) and 5′ → 3′ exonuclease
activity.
DNA repair
Elimination of DNA mutations to maintain stability of the
genome. Facilitated by the NHEJ, homologous recombination,
and nucleotide excision pathways.
DNA vaccination
Immunization with plasmid DNA to induce an adaptive
immune response against the encoded protein. Bacterial
DNA, which is rich in unmethylated CpG dinucleotides,
serves as an adjuvant for this kind of vaccination.
DNA vaccine
An immunizing preparation composed of a bacterial
plasmid containing a cDNA encoding a protein antigen.
The mechanism apparently consists of professional
antigen-presenting cells transfected in vivo by the
plasmid which then express immunogenic peptides that
induce specific immune responses. The CpG nucleotides
present in the plasmid DNA serve as powerful adjuvants.
DNA vaccines may induce strong cytotoxic T lymphocyte
responses. This is an immunizing preparation
prepared by genetic engineering methods in which the
gene that encodes an antigen is inserted into a bacterial
plasmid, which is injected into the host. Once inside, the
gene employs the nuclear machinery of the host cell to
manufacture and express the antigen. In contrast to other
vaccines, DNA vaccines may induce cellular as well as
humoral immune responses.
DNBS (2,4-dinitrobenzene sulfonate)
A substance employed to generate dinitrophenylated
proteins used as experimental antigens. Chemically, DNBS
reacts principally with lysine residue-free ε amino groups if
an alkaline pH is maintained.
DNCB
Refer to dinitrochlorobenzene.
DNP
Refer to dinitrophenyl group.
DO and DM
Major histocompatibility complex (MHC) class II-like
molecules. DO gene expression occurs exclusively in the
thymus and on B lymphocytes. DNα and DOβ chains pair
to produce the DO molecule. Information related to DM
gene products awaits further investigation.
doctrine of original antigenic sin
The immune response against a virus, such as a parental
strain, to which an individual was previously exposed may
be greater than it is against the immunizing agent, such as
type A influenza virus variant. This concept is known as
the doctrine of original antigenic sin.
P P P OH + P OH + P OH P P P P P OH
P
P
P
P
Activity of terminal deoxnucleotidyl transferase (TdT).
D