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College Biology1
Biology - Ch16
| Term | Definition |
|---|---|
| dna replication | The process by which a DNA molecule is copied; also called DNA synthesis. |
| transformation | (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer. |
| bacteriophages | A virus that infects bacteria; also called a phage. |
| phages | A virus that infects bacteria; also called a bacterial phage. |
| virus | An infectious particle incapable of replicating outside of the cell, consisting of an RNA or GNA genome surrounded by a protein cote (capsid) and, for some viruses, a membraneous envelope. |
| double helix | The form of native DNA, referring to it’s two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape. |
| antiparallel | Referring to the arrangement of the sugar phosphate backbones in a DNA double helix. |
| semiconservative model | type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand. |
| origins of replication | Site where the replication of DNA molecules begins, consisting of a specific sequence of nucleotides. |
| replication fork | A Y shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized. |
| helicases | An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands. |
| single strand binding proteins | 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. |
| 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. |
| primer | a short stretch of RNA with a free 3’ end, bound by complimentary base pairing to the template strand and elongated with DNA nucleotides during DNA replication. |
| primase | An enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strands as a template. |
| dna polymerases | An enzyme that catalyzes the elongation of new DNA by the addition of nucleotides to the 3’ end of an existing chain. There are several different DNA polymerases; DNA polymerase 3 and DNA polymerase 1 play a major role in DNA replication in e.coli. |
| leading strand | the new complimentary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5’ ----> 3’ direction. |
| 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. |
| okazaki fragments | A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of the newly synthesized DNA. |
| dna ligase | A linking enzyme essential for DNA replication; catalyzes the covalent bonds of the 3’ and of one DNA fragment (such as an Okazaki fragment) to the 5’ end of another DNA fragment (such as a growing DNA chain) |
| 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 |
| nucleotide excision repair | A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide. |
| telomeres | The tandemly repetitive DNA at the end of a eukaryotic chromosome(s) DNA molecule. Telomeres protect the organism(s) genes from being eroded during successive rounds of replication. |
| telomerase | An enzyme the catalyzes the lengthening of telomeres in eukaryotic germ cells. |
| nucleoid | A non membrane bounded region in a prokaryotic cell where the DNA is concentrated. |
| chromatin | The complex of DNA and proteins that make up eukaryotic chromosomes. 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. |
| histones | A small protein with a high proportion with positively charged amino acids that bind to the negatively charged DNA and play a key role in the chromatin structure |
| 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 the four types of histone. |
| heterochromatin | Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed. |
| euchromatin | The less condensed form of eukaryotic chromatin that is available for transcription. |
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lizhopper2
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