AP Biology, Campbell 7e
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| 641273350 | bacteria | One of two prokaryotic domains, the other being Archaea. | |
| 641273351 | bacteriophage | A virus that infects bacteria; also called a phage. | |
| 641273352 | bacterium | Member of the prokaryotic domain Bacteria. | |
| 641273353 | 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. | |
| 641273354 | deoxyribose | The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides. | |
| 641273355 | 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). | |
| 641273356 | 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. | |
| 641273357 | double helix | The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape. | |
| 641273358 | euchromatin | The less condensed form of eukaryotic chromatin that is available for transcription. | |
| 641273359 | 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. | |
| 641273360 | heterochromatin | Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed. | |
| 641273361 | 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. | |
| 641273362 | 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. | |
| 641273363 | Leading strand | The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5'?3' direction. | |
| 641273364 | Mismatch repair | The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides. | |
| 641273365 | 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. | |
| 641273366 | nucleoid | A dense region of DNA in a prokaryotic cell. | |
| 641273367 | nucleoid region | A dense region of DNA in a prokaryotic cell. | |
| 641273368 | 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. | |
| 641273369 | nucleotide excision repair | A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide. | |
| 641273370 | 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. | |
| 641273371 | origin of replication | Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides. | |
| 641273372 | phage | A virus that infects bacteria; also called a bacteriophage. | |
| 641273373 | primase | An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template. | |
| 641273374 | primer | A short stretch of RNA with a free 3' end, bound by complementary base pairing to the template strand, that is elongated with DNA nucleotides during DNA replication. | |
| 641273375 | 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. | |
| 641273376 | radioactive isotope | An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy. | |
| 641273377 | 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. | |
| 641273378 | replication fork | A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are growing. | |
| 641273379 | 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. | |
| 641273380 | Single-strand DNA-binding protein (SSBPs) | 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. | |
| 641273381 | telomerase | An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells. | |
| 641273382 | 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. | |
| 641273383 | template strand | The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript. | |
| 641273384 | 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. | |
| 641273385 | 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. | |
| 641273386 | 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. |
