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

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