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35 Cards in this Set

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bacteriophage
A virus that infects a bacteria; also called a phage.
chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.
deoxyribose
The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of one DNA fragment (such as an Okazaki fragment) to the 5' end of another DNA fragment (such as a growing DNA chain).
DNA polymerase
An enzyme that catalyzes the elongation of new DNA (for example, at a replication fork) by the addition of nucleotides to the 3' end of an existing chain. There are several different DNA polymerases; DNA polymerase III and DNA polymerase I play major roles in DNA replication in prokaryotes.
double helix
The form of native DNA, referring to its two adjacent antiparallel polynucleotide strand wound around an imaginary axis into a spiral shape.
euchromatin
The less condensed form of eukaryotic chromatin that is available for transcription.
helicase
An enzyme that untwists the double helix of DNA at the replication forks, separating the two strands and making them available as template strands.
heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
histone
A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in chromatin structure.
histone
A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in chromatin structure.
lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5'-3' direction away from the replication fork.
leading strand
The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5'-3' direction.
mismatch repair
The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.
nuclease
An enzyme that cuts DNA or RNA, either removing one or a few bases or hydrolyzing the DNA or RNA completely into its component nucleotides.
nucleoid
A dense region of DNA in a prokaryotic cell.
nucleoid region
A dense region of DNA in a prokaryotic cell.
nucleosome
The basic, bead-like unit of DNA packing in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histone.
nucleotide excision repair
A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.
Okazaki fragment
A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication, many of which are joined together to make up the lagging strand of newly synthesized DNA.
origin of replication
Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.
phage
A virus that infects bacteria; also called a bacteriophage.
primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
pyrimidine
One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C), thymine (T), and uracil (U) are pyrimidines.
radioactive isotope
An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.
repetitive DNA
Nucleotide sequences, usually noncoding, that are present in many copies in a eukaryotic genome. The repeated units may be short and arranged tandemly (in series) or long and dispersed in the genome.
replication fork
A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are growing.
semiconservative model
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.
single-strand binding protein
A protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA.
telomerase
An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.
telomere
The tandemly repetitive DNA at the end of a eukaryotic chromosome’s DNA molecule that protects the organism’s genes from being eroded during successive rounds of replication. See also repetitive DNA.
template strand
The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript.
topoisomerase
A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, topoisomerase helps to relieve strain in the double helix ahead of the replication fork.
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
X-ray crystallography
A technique that depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule to study the three-dimensional structure of the molecule.