| A | B |
|---|
| deoxyribonucleic acid (DNA) | A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins. |
| euchromatin | The more open, unraveled form of eukaryotic chromatin that is available for transcription. |
| heterochromatin | Nontranscribed eukaryotic chromatin that is so highly compacted that it is visible with a light microscope during interphase. |
| double helix | The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape. |
| nucleotides, nucleotide | The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. |
| nitrogenous base | a key component of a nucleotide such as adenine, guanine, cytosine, thymine |
| deoxyribose | The sugar component of DNA, having one less hydroxyl group than ribose, the sugar component of RNA. |
| adenine | a purine ( double-ringed nitrogenous base) |
| guanine | a purine ( double-ringed nitrogenous base) |
| cytosine | a pyrimidine (single-ringed nitrogenous base) |
| thymine | a pyrimidine ( singled-ringed nitrogenous base) |
| phosphodiester bonds | how nucleotides link themselves together |
| base pairing | the predictable matching of the bases |
| complementary | Of or relating to the specific pairing of the purines and pyrimidines between strands of a DNA or an RNA molecule. |
| antiparallel | two DNA strands that run in opposite directions |
| hydrogen bonds, hydrogen bond | A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule. |
| ribonucleic acid (RNA) | A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses. |
| DNA replication | the copying of DNA |
| helicase | An enzyme that untwists the double helix of DNA at the replication forks. |
| replication fork | A Y-shaped region on a replicating DNA molecule where new strands are growing. |
| topoisomerase | cuts and rejoins the helix to prevent tangling |
| origins of replication | Sites where the replication of a DNA molecule begins. |
| DNA polymerase | An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain. |
| RNA primase | a short strand of RNA nucleotides |
| leading strand | The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' 3' direction. |
| lagging strand | A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork. |
| Okazaki fragments | lagging strand made in pieces of nucleotides |
| DNA ligase | A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 39 end of a new DNA fragment to the 59 end of a growing chain. |
| semiconservative | 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. |
| ribose | The sugar component of RNA. |
| uracil | replaces thymine |
| mRNA | A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein. |
| rRNA | The most abundant type of RNA, which together with proteins, forms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons. |
| tRNA | An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA. |
| protein synthesis | the process by which amino acids are linearly arranged into proteins through the involvement of ribosomal RNA, transfer RNA, messenger RNA, and various enzymes. |
| transcription | The synthesis of RNA on a DNA template. |
| translation | The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids. |
| promoters | A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA. |
| sense strand | strand that serves as the template |
| antisense strand | strand that lies dormant |
| RNA polymerase | An enzyme that links together the growing chain of ribonucleotides during transcription. |
| processed | mRNA has to be modified before it exits the nucleus |
| exons | A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns. |
| introns | A noncoding, intervening sequence within a eukaryotic gene. |
| poly (A) tail | The modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides. |
| 5'cap | The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide. |
| codons | A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code. |
| anticodon | A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule. |
| A site | One of three binding sites for tRNA during translation, it holds the tRNA carrying the next amino acid to be added to the polypeptide chain; A stands for aminoacyl-tRNA site. |
| P site | One of three binding sites for tRNA during translation, it holds the tRNA carrying the growing polypeptide chain; P stands for peptidyl-tRNA site). |
| peptide bond | The covalent bond between two amino acid units, formed by a dehydration reaction. |
| polypeptide | A polymer (chain) of many amino acids linked together by peptide bonds. |
| stop codon | a codon that stops the synthesis of a protein molecule. |
| protiens | A three-dimensional biological polymer constructed from a set of 20 different monomers called amino acids. |
| primary structure | The level of protein structure referring to the specific sequence of amino acids. |
| secondary structure | The localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between peptide linkages. |
| tertiary structure | Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges |
