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35 Cards in this Set
- Front
- Back
bacteriophage
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A virus that infects a bacteria; also called a phage.
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chromatin
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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.
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deoxyribose
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The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides.
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DNA ligase
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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).
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DNA polymerase
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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.
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double helix
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The form of native DNA, referring to its two adjacent antiparallel polynucleotide strand wound around an imaginary axis into a spiral shape.
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euchromatin
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The less condensed form of eukaryotic chromatin that is available for transcription.
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helicase
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An enzyme that untwists the double helix of DNA at the replication forks, separating the two strands and making them available as template strands.
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heterochromatin
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Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
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histone
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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.
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histone
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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.
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lagging strand
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A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5'-3' direction away from the replication fork.
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leading strand
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The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5'-3' direction.
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mismatch repair
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The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.
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nuclease
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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.
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nucleoid
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A dense region of DNA in a prokaryotic cell.
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nucleoid region
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A dense region of DNA in a prokaryotic cell.
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nucleosome
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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.
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nucleotide excision repair
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A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.
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Okazaki fragment
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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.
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origin of replication
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Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.
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phage
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A virus that infects bacteria; also called a bacteriophage.
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primase
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An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
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pyrimidine
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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.
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radioactive isotope
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An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.
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repetitive DNA
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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.
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replication fork
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A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are growing.
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semiconservative model
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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.
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single-strand binding protein
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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.
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telomerase
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An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.
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telomere
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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.
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template strand
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The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript.
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topoisomerase
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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.
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transformation
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(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.
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X-ray crystallography
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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.
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