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BIO205 - CH8 - Microbial Genetics - Tortora - Rio Salado - AZ

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Question
Answer
Genetic info in a cell   Genome - includes chromosomes & plasmids  
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DNA made of?   Nitrogenous base (A-T, G-C), deoxyribose (pentose sugar) & a phosphate group  
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Sugar-phosphate backbone   Alternating sugar & phosphate group  
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Where is base attached in DNA?   To each sugar in backbone  
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What constitutes phenotype in molecular terms?   Its collection of proteins - both enzymatic & structural  
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genotype   refers to the particular alleles individual carries  
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phenotype   refers to an individual's observable traits  
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semiconservative replication   Each DNA molecule - on strand is from the starting molecule, so it's said to be conserved, only the 2nd strand has been freshly synthesized. 1/2 new, 1/2 old  
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DNA polymerases   Enzymes that unwind DNA molecule, keep the 2 unwound, & assemble new strand on each one - link individual nucleotides on parent strand.  
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DNA ligases   Enzyme that seals new base-pairing during DNA replication - also used by recombinant DNA techs to seal base-pairings between DNA fragments & cut plasmid DNA.  
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Base pairs   2 kinds in DNA = A-T & G-C  
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gene   sequence of nucleotides in DNA  
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DNA'S nucleotides are built of ___.   sequences of nucleotides in DNA  
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nucleotide   Building blocks of nucleic acids, composed of phosphate & nitrogen-containing base (A,G,T,or C)  
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thymine dimers   UV light causes two neighboring thymine bases to become linked (a dimer) - distorts affected DNA molecule & increases chance for replication errors.  
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RNA polymerases   Enzyme that catalyzes the assembly of RNA strands on DNA templates.  
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promoter   a sequence of bases that signals the start of a gene  
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5'   Capped end where mRNA will bind to a ribosome when time comes for translation. Phosphate end attached to carbon  
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3'   the trailing end of the forming RNA molecule - hydroxyl end attached to carbon  
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5' ---> 3'   The direction of one DNA strand that runs counter to the other  
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Sequencing of molecular characterization of genomes.   Genomics  
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Supercoiling on DNA relaxed by? Unwound by?   Gyrase or topoisomerase, helicase  
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Enzyme that joins nucleotide to DNA strand.   DNA polymerase  
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Point at which replication occurs   replication fork  
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1'   One prime = carbon atoms of sugar in each nucleotide  
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DNA polymerases can only add nucleotides to the __.   3' end  
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DNA strands grow in different __.   directions  
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Where does energy come from to replicate DNA?   The nucleotides - 2 phosphate groups removed to add nucleotide to DNA - hydrolysis makes new bond.  
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Leading strand   The new DNA strand being synthesized in 5' -- 3' direction.  
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Which enzyme has proofreading capability?   DNA polymerase - evaluates if proper base-pairing structure.  
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DNA replication sequence - 6 steps   (1) helicase unwinds & rep fork form @ orig, (2) proteins stabilize, (3) Lead strand synth by DNA polymer. (5' -3'), (4) lag strand synth discontinously (RNA primer(5) RNA primer digest by DNA polymer. & replaced w/DNA, (6) DNA ligase joins new DNA fragm.  
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RNA   Ribonucleic acid - ribose (sugar), a phosphate group & base - A,C,G & U (uracil).  
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ribosomal RNA (rRNA)   Nuclic acid chain that combines w/certain proteins to form a ribosome, a structure on which a polypeptide chain is assembled.  
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messenger RNA (mRNA)   A linear sequence of nucleotides that carries protein-building instructions; this "code" is delivered to the ribosome for translation into a polypeptide chain.  
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transfer RNA (tRNA)   Another nucleic acid chain that can pick up a specific amino acid & pair with an mRNA code word for that amino acid.  
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Which comes 1st, translation or transcription?   Transcription - genetic info in DNA transcribed into RNA.  
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Synthesis of complementary RNA strand.   transcription  
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Which RNA carries coded info to ribosomes?   in RNA  
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Transcription requires what enzyme?   RNA polymerase  
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RNA polymerase binds to DNA where?   at promoter  
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Another name for protein synthesis   translation  
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language of mRNA   codons  
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Each codon codes for what?   A particular amino acid  
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__ refers to fact that most amino acids are signaled by several alternate codons.   degeneracy of the code  
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Start codon   methionine - AUG  
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Each tRNA has an __.   anticodon  
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Function of ribosome is to directly orderly binding of __ to __ & assemble __.   tRNA, codons, amino acids  
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Different locations of transcription between Prokaryote & Eukaryote   prok=cytoplasm, euk=nucleus  
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Eukaryote RNA molecule containing introns & exons.   RNA transcript  
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Products constantly produced at fixed rate.   constitutive  
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Name 2 genetic control mechanisms   repression & induction  
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How does repression work?   Inhibits gene expression by repressor (reg proteins) that block RNA polymerase's ability to initiate transcription  
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The process that turns on gene transcription.   induction  
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How does induction work?   Inducer (enzyme) encourages cell to synthesize more enzymes.  
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Repressible gene is default __ while inducible gene is default __.   on, off  
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Structural genes   Determine the structures of proteins - amino acid sequence  
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operon   Operator & promoter sites & the structural genes they control.  
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operator   Region of DNA adjacent to structural genes that control their transcription.  
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Promoter   Starting site on DNA strand for transcription of RNA by RNA polymerase  
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Details of the control of gene expression by induction & repression are described by __.   operon model  
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What combines to form lac operon?   3 lac structural genes & adjoining control regions.  
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I gene codes for what in bacterial DNA?   Repressor protein - blocks ability of RNA polymerase to initiate transcription.  
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Repressor protein binds & prevents RNA polymerase when __.   the necessary substance - like lactose - is absent.  
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Why are enzymes produced in presence of lactose?   Some lactose is transported into cell & is converted into an inducer, which binds to repressor protein & alters it, allowing operator site to be open.  
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Corepressor do what?   Bind to repressor protein & allow it to bind to operator to repress synthesis.  
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Transcription of the lac operon requires?   Presence of lactose & absence of glucose.  
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Catabolite repression (glucose effect)   INhibition of alternate carbon sources for metabolism due to availability of glucose.  
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Base substitution that results in amino acid substitution in synthesized protein.   Missense mutation - change in DNA due to base substitution.  
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Sickle cell disease due to __ mutation.   missense  
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Mutation in base substitution that causes a stop codon to be in wrong place.   Nonsense mutation - only a fragment of the protein is made.  
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What does nitrous acid do to DNA?   Chemical mutagen - makes base-pair changes and alters DNA.  
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Nucleoside analog   Chemical that is structurally similar to normal nucleosides in nucleic acids, but with altered base-pairing properties.  
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Frameshift mutagens are often __.   potent carcinogens  
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Why are X rays & gamma rays potent mutigens?   They have rays of ionizing radiation that cause electrons to pop out of their shells & become ions & free radicals.  
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Mutagens increase rate of?   Spontaneous mutation by 10 - 1000 times.  
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Positive (direct) selection   Identifying mutant cells by culturing them.  
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Negative (indirect) selection   Identifying mutant cells by selecting cells that don't grow using replica plating.  
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replica plating   Inoculating a number of solid minimal culture media from an original plate to produce same pattern of colonies on each plate.  
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What is an auxotroph?   A mutant microbe having a nutritional requirement that is absent in parent - enzyme lacking, etc.  
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An Ames test is used to screen?   For potential carcinogens - uses bacteria.  
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Plants & animals transmit their genes by __ gene transfer.   vertical - passing genes to offspring.  
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Bacteria can pass thier genes __.   horizontally - to other microbes of same generation.  
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In horzontal gene transfer, who is the recombinant?   The recipient cell that incorporates donor DNA into its own DNA.  
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What is transformation in bacteria?   Genes are transferred from one bacteria to another as "naked" DNA.  
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Competence results from __.   alterations in cell wall that make it permeable to large DNA molecules.  
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Conjugation   Plasmid replicates independently from cell's chromosome.  
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Conjugation requires __.   direct cell-to-cell contact.  
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F factor   Fertility factor - a plasmid found in donor cell in bacterial conjugation.  
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Hfr cell   F+ factor integrates into chromosome & creates - high frequency of recombination.  
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__ is used to map location of genes on bacterial chromosomes.   conjugation  
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Transduction   Bacterial DNA transferred from donor to recipient cell inside a virus that infects bacteria. Bacteriophage, or phage.  
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What mechanism of genetic transfer creates phage?   Transduction  
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Name 4 ways bacteria can acquire new genotypes.   Mutation, transformation, conjugation, & transduction.  
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The F factor is a __.   conjugate plasmid - carries gene for sex pili.  
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__ plasmids code for enzymes that trigger catabolism of unusual sugars & hydrocarbins.   dissimilation  
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Dissimilation plasmids help bacteria to __.   survive in very diverse & challenging environments  
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Bacteriocins   toxic proteins that kill other bacteria.  
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Resistance factors (R factors)   Carry genes that confer resistance to antibiotics, heavy metals, toxins.  
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transposons   Small DNA segments that move around on a DNA molecule.  
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Insertion sequences (IS)   Contain a gene that codes for an enzyme which catalyzes cutting & resealing of DNA during transposition.  
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Plasmids like R factors are frequently made up of __.   a collection of transposons  
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Transposons can spread from __.   one organism - or even speces - to another.  
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A powerful mediator of evolution in an organism.   transposons.  
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