Life 205 Chpt. 7 – Flashcards
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| What are the three functional types of RNA molecules? |
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| 1.Messenger RNA (mRNA) 2.Transfer RNA (tRNA) 3.Ribosomal RNA (rRNA) |
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| Most genes encode proteins that are transcribed into what? |
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| mRNA |
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| The complete set of genetic info in a cell is referred to as what? |
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| The genome |
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| the process of gene expression involves what two inter-related events? |
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| Transcription translation |
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| the process copies the info encoded in DNA into RNA. |
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| Transcription |
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| This process interprets info carried by RNA to synthesize the encoded protein. |
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| Translation |
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| A complex of enzymes and other proteins that synthesize DNA. (In an "assembly line") |
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| Replisomes |
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| This enzyme temporarily breaks the strands of DNA, relieving the tension caused by unwinding the 2 strands of the DNA helix. |
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| DNA Gyrase (stops the gyrating of the DNA) |
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| This enzyme joins 2 DNA fragments by forming a covalent bond btwn the sugar and phosphate residues of adjacent nucleotides. |
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| DNA Ligase |
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| This enzyme synthesizes DNA. |
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| DNA polymerases |
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| What direction does synthesis always occur? |
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| 5' to 3' direction. |
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| In DNA synthesis, nucleotides can only be added to what end of the existing fragment? |
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| The 3' end. |
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| These enzymes unwind the DNA helix ahead of the replication fork. |
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| Helicases |
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| Nucleic acid fragment produced during discontinuous synthesis of the lagging strand of DNA. |
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| Okazaki fragments. |
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| The distinct region of a DNA molecule at which replication is initiated. |
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| Origin of replication |
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| Enzyme that synthesizes small fragments of RNA to serve as primers for DNA synthesis. |
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| Primase |
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| A fragment of nucleic acid to which DNA polymerase can add nucleotides. (to an existing fragment only) |
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| Primer |
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| In transcription, this enzyme synthesizes single-stranded RNA molecules from a DNA template. |
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| RNA polymerase |
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| The DNA sequence to which RNA polymerase can bind and initiate transcription is called what? |
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| A promoter |
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| A DNA sequence that stops the process of transcription. |
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| terminator |
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| What is one major difference btwn RNA polymerase and DNA polymerase? |
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| RNA polymerase can start transcription without a primer. |
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| The DNA strand that serves as the template for transcription. |
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| The Minus(-) strand |
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| The complement of the minus strand |
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| The plus (+) strand |
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| T or F, In prokaryotes, mRNA molecules can carry the info for one or multiple genes? |
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| True |
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| A transcript that carries one gene. |
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| monocistronic |
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| a transcript that carries multiple genes |
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| polycistronic |
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| This is a component of RNA polymerase that recognizes the promoter regions. A cell can have different types that recognize different promoters, allowing the cell to transcribe specialized sets of genes as needed. |
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| A sigma factor |
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| These identify the regions of the DNA molecule that will be transcribed into RNA. They orient the direction of the RNA polymerase and dictate which strand will be used as the template. |
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| Promoters |
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| What occurs in the elongation phase? |
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| RNA polymerase moves along DNA using the (-) strand as a template to synthesize a single-stranded RNA molecule. |
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| Once elongation has proceeded far enough for RNA polymerase to clear the promoter, what can happen? |
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| A new RNA enzyme can bind, thus a single gene can be transcribed repeatedly very quickly. |
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| What three structures are required for translation? |
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| mRNA, ribosomes, and tRNA's. |
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| What direction does the ribosome move on the mRNA? |
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| the 5' to 3' direction. |
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| what are prokaryotic ribosomes composed of? |
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| a 3OS subunit and a 5OS subunit each made up of a protein and ribosomal RNA. |
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| WHat are the two sites on a ribosome that tRNA can bind? What happens when they are both occupied by a tRNA? |
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| The P-site and the A-site. When both are filled, an enzyme creates a peptide bond btwn the two amino acids. |
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| the site through which the initiating tRNA is released. |
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| The E-site |
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| an assembly of multiple ribosomes attached to a single mRNA molecule. |
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| polyribosome, or polysome |
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| Proteins that assist in the folding of polypeptides. |
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| Chaperones |
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| How can the cell tell if a polypeptide is destined for transport through the cytoplasmic membrane? |
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| It will have a signal sequence which is a characteristic series of hydrophobic amino acids that tags them for transport. |
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| What are the four main differences btwn prok and euk gene expression? |
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| Eukaryotic pre-mRNA must be processed. This involves capping, polyadenylation, and splicing. It must also be transferred out of the nucleus before it can be translated in the cytoplasm. Eukaryotic mRNA is monocystronic. |
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| This transmits information from outside the cell to the inside. |
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| signal transduction |
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| Some organisms can "sense" the density of cells within their own population. this is called what? |
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| quorum sensing |
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| THis allows cells to activate genes that are only useful when expressed by a critical mass |
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| quorum sensing (e.g. biofilms) |
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| an important mechanism that cells use to detect and react to changes in the external environment. |
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| two-component regulatory system |
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| an alteration in the characteristics of certain surface proteins in a bacterial cell. |
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| antigenic variation |
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| what allows pathogens to stay one step ahead of the body's defense by altering the molecules our immune systems recognize? |
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| antigenic variation |
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| What is the routine switching on and off of certain genes? |
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| phase variation |
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| A set of regulated genes transcribed as a single polycystronic message. |
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| an operon |
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| separate operons controlled by a single regulatory mechanism constitute a what? |
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| regulon |
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| The simultaneous regulation of numerous genes is called what? |
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| global controll |
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| this type of enzymes are synthesized constantly; the genes that encode them are always active. (enzymes of glycolysis) |
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| constitutive |
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| synthesis of this type of enzyme is turned on when needed. (Beta-galactoisade) |
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| inducible |
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| these enzymes are produced routinely, but their synthesis can be turned off when they are not required. (generally enzymes used in anabolic pathways) |
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| repressible |
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| when glucose is available, the lac operon is not expressed because of a phenom called what? |
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| Carbon catabolite repression (CCR) |
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| The two-phase growth pattern between the use of glucose and other carbon /energy sources. |
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| diauxic growth |
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| One mechanism of carbon catabolic repression involves an activator called _____ that is bound by an inducer cAMP. |
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| CAP (catabolite activator protein) |
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| In the eukaryotic cell, this is routinely used to destroy specific RNA transcripts |
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| RNAi (interference RNA) |
