Download GLOSSARY Adenine : (6-aminopurine)

GLOSSARY
Adenine
:
(6-aminopurine)
-
a
nitrogenous
base
derived from amino acids and sugars and is
basic constituent of DNA, RNA, ATP etc.
Antiparallel
: Two linear polymers that are opposite in
polarity or orientation.
Cell
: Fundamental unit of living organism and the
basis of its structure and physiology.
Chromosome :
Thread-like structure having genetic
material of organism made up of chromatin
and becomes visible under light microscope
prior to nuclear division due to condensation
of chromatin.
Cytosine
: (4-amino, 2-oxypyrimidine) a crystalline
pyrimidine base obtained by hydrolysis of
DNA.
DNA
:
(Deoxyribonucleic
acid)
-
hereditary
substance in living organisms. It is mostly
found in chromosomes in association with
histones in eukaryotes while it is naked
forming circles or loops in prokaryotes.
DNA ligase
: An enzyme that catalyses the linking of
two molecules.
DNA polymerase : A group of enzymes that catalyses
the polymerization assisting in the formation
of DNA.
DNA supercoiling: The coiling of DNA upon itself, as a
result of bending, under-winding or overwinding of the DNA helix.
Eukaryotes
: Organisms with cells that have nuclear
material surrounded by and separated from
cytoplasm by a definite nuclear membrane.
Exonuclease : Enzyme that detaches a nucleotide from
nucleic acid (DNA) to break it down by
hydrolysis.
Genome
:
Complete
set
of
haploid
number
of
chromosomes in an organism.
Guanine
: (2-amino, 6-oxypurine) a crystalline purine
derivative obtained by hydrolysis of DNA.
Helicase
: An enzyme that catalyses the separation of
strands in a DNA molecules before replication
.
Interphase
: Period during cell division following
cytokinensis till next nuclear division.
Isotope
: Two or more forms of chemical element with
different relative atomic mass and different
nuclear but not chemical properties.
Lagging strand
:
The
DNA
strand
that
during
replication, is synthesized in the direction
opposite to that in which the replication fork
moves.
Leading strand
:
replication,
The
is
DNA
strand
synthesized
that,
in
the
during
same
direction in which the replication fork moves.
Mitosis
: Nuclear division in which nucleus of cell
divides to form two daughter nuclei having
same number of chromosomes as original
nucleus.
Monomer : A substance composed of small molecules
which under the proper conditions may unite
to form a polymer.
Nucleoid
: In bacteria, the nuclear zone that contains
the chromosome but has no surrounding
membrane.
Nucleoside
: Base sugar complex formed when purine
or pyrimidine base combines with carbon 1 of
pentose sugar.
Nucleus
: Cell organelle in eukaryotic cell that contains
genetic material (chromatin) and nucleoplasm
surrounded by nuclear membrane.
Pentose sugar
: The 5-carbon sugar, e. g. ribose,
deoxyribose etc.
Phosphate : Any salt or ester of phosphoric acid.
Phosphodiester
bond
: A chemical grouping that contains two
alcohols
esterified
to
one
molecule
of
phosphoric acid, which thus serves as a
bridge between them.
Polynucleotide
: A covalently linked sequence of
nucleotides
in
which
3
hydroxyl
of
the
pentose sugar of one nucleotide residue is
joined by a phosphodiester bond to the 5
hydroxyl of the pentose sugar of the next
residue.
Primase
: An enzyme that catalyses the formation of
RNA oligonucleotides used as primers by DNA
polymerases.
Primer
: A short oligomer (e, g. of sugars or
nucleotides)
to
which
an
enzyme
adds
additional monomeric subunits.
Prokaryotes
: Organisms with cells in which nuclear
material is not separated from cytoplasm by
nuclear membrane.
Purine
:
Nitrogen
containing
organic
base
synthesized mainly from amino acids. Two
purines-
adenine
and
guanine
are
constituents of nucleotides.
Pyrimidine
: A nitrogenous heterocyclic base found in
nucleotides
and
nucleic
acids;
the
two
pyrimidines are- Thymine and Cytosine.
Replication
: Formation of exact copies (replicas).
Replicon
: Individual unit of replication.
RNA
:
(Ribonucleic
acid)
-
single
stranded
nucleotide polymer; each nucleotide made up
of phosphoric acid, ribose sugar and one of
the four bases (Adenine, Guanine, Cytosine
and Uracil).
RNA polymerase : A group of enzymes that catalyses
polymerization assisting in the formation of
RNA.
Semi conservative
replication: Process by which DNA makes exact copies of
a self involving uncoiling of double stranded
DNA molecule.
S-phase
:
Period
replication
during
takes
cell
division
place
(as
when
DNA
chromosomes
divide into chromatids.
Template : A macromolecular mold or pattern for the
synthesis of an informational molecule.
Thymine
:
(5-methyl,
crystalline
2-4,
pyrimidine
dioxypyrimidine)
base
obtained
a
by
hydrolysis from DNA.
Topoisomerase
: Enzymes that introduce positive or
negative super coils in closed circular duplex
DNA.
Uracil
: (2-4, dioxypyrimidine) a pyrimidine base
obtained by hydrolysis of RNA (and replaced
by Thymine in DNA).
X-ray
crystallography
: The analysis of x-ray diffraction
patterns of a crystalline compound, used to
determine the molecule’s three dimensional
structure.