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