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Ch. 18 Microbial Models: The Genetics of Viruses and Bacteria & Ch. 20 DNA Technology and Genomics

STUDY
PLAY
virus
parasite that can live only inside another cell; commandeers the host cell machinery to transcribe and translate all the proteins it needs to make copies of itself; consists of DNA/RNA enclosed in protein coat; gains entry into cell through special receptors, causing it to be limited to one specific cell type
capsid
protein coat that bacterial DNA or RNA is enclosed by
viral envelope
found in some viruses, it is derived from the membrane of host cells, and it cloaks the capsid and aids the virus in infecting the host
host range
the range of organisms that a cirus can attack; mutations in the virus can expand this
bacteriophages
the most complex and best understood virus is this one, which infects bacteria. It can reproduce with either the lytic cycle or lysogenic cycle
lytic cycle
cycle where phage enters host cell, takes control of the cell machinery, replicates itself, and then causes the cell to burst (EXPLOSION!!!!!), releasing a new generation of infectious phage viruses
lysogenic cycle
virus replicates without destroying the host cell. The phage virus remains dormant at specific site in the host DNA. As the host cell divides, the phage is replicated and infection spreads until an environmental trigger switches it to the other cycle's phase
prophage
the state in which the phage virus remains dormant at a specific site in the host DNA
lytic phase
environmental trigger causes prophage of lysogenic cycle to switch into this phase
temperate viruses
viruses capable of both modes of reproducing, lytic and lysogenic, within a bacterium
retroviruses
viruses that contain RNA instead of DNA and replicate in an unusual way. RNA serves as a template for synthesis of complementary DNA (cDNA); reverses flow of information from the usual DNA to RNA sequence using reverse transcription. Usually permanent prophage and can make multiple viral genome copies
reverse transcriptase
the enzyme involved in reverse transcription in retroviruses which reverse the flow of information from DNA to RNA
transduction
phae virsuses acquire bits of bacterial DNA as they infect one cell after another, leading to genetic recombination
generalized transduction
the moving of random pieces of bacterial DNA as the phage lyses one cell and infects another during the lytic cycle
specialized (restriced) transduction
transfer of specific pieces of DNA. During lysogenic cycle, phage integrates into host cell at certain site. When the phage later ruptures out of the host DNA, it might carry a piece of adjacent host DNA with it and insert host DNA into next host it infects
nucleoid
the bacterial chromosome that is a circular, double-stranded DNA molecule with no nuclear membrane
both; single point of origin; theta replication
Bacteria replicate in _______ directions and from ______________ by a process of _____________
conjugaton
primitive sexual method; not the main mode
binary fission
main mode of reproduction that is asexual; results in population with identical genes (with some mutations)
bacterial transformation
Griffith discovered with his experiments with R & S strains of bacteria. It is the process that provides a mechanism for the recombination of genetic information in some bacteria. A genetic change takes place in the cell where the extracellular DNA is taken up
plasmid
foreign, small, circular, self-replicating DNA that inhabits a bacterium; bacterium express the genes carries by this
pili
F plasmids contain genes for production of these cytoplasmic brdiges that connect to an adjacent cell and that allow DNA to move from one cell to another through conjugation
R plasmid
carry the genes for antibiotic resistance
operon
unit of DNA that controls the transcription (expression) of a gene: contains promoter, operator, structural genes, and regulatory genes
promoter
a region where RNA polymerase attaches, it is used in regulation of gene expression on the operon. It is a sequence of DNA to which the RNA polymerase attaches to begin transcription
operator region
region used in regulation of gene expression on the operon. It blocks the action of the RNA polymerase if this region is occupied by a repressor protein
structural genes
contain DNA sequences that code for several related enzymes that direct the production of some particular end product
regulatory gene
it lies outside the operon region, produces repressor proteins. They also make activator proteins.
repressor proteins
they are made by the regulatory gene and they occupy the operator region and block the binding of RNA polymerase
activator proteins
they are made by the regulatory gene and assist the attachment of RNA polymerase to the promoter region
inducible
Lac operon; one type of operon which is switched OFF until it's induced to turn on. 3 enzymes are coded for in this operon
repressible
trytophan operon; one type of operon that allows RNA polymerase to bind to the promoter and transcribe structual genes because it is always in ON position until not needed and thus becomes repressed by a corepressor. It has 5 structural genes that code for enzymes to make trytophan, the corepressor that binds with an inactive repressor which binds w/ the operator and stop RNA polymerase
noncompetitive inhibition
both substances compete for 2 active sites; exemplified by the relationship between RNA polyermerase and the repressor
allolactose
it is similar to lactose, making it an inducer or allosteric effector that can bind to the repressor and cause it to change shape and prevent the repressor from blocking RNA polymerase
trytophan
amino acid that acts as a corepressor and allosteric effector because it binds to the repressor which binds to the operator and stops RNA polymerase from binding to the promoter and making the structural genes
prions
not cells or viruses but are misfoldded proteins normally in the brain; they cause disease like mad cow disease or Creutzfeldt-Jakob disease for humans
transposons
discovered by Barbara McClintock, they are transposable genetic elements that are also called jumping genes. They jump in a cut-and-paste fashion from one part of the genome to another, creating either insertion sequences or complex ___________
insertion sequences
one type of transposon that have only one gene which codes for transposase
transposase
enzyme existing in insertion sequnces for moving the sequence from one place to another; can cause mutation if in DNA region that regulates gene expression
complex transposon
one type of transposon that is longer than insertion sequence and have extra genes for antibiotic resistance, seed color, etc.; discovered by McClintock who saw this in corn
junk
human DNA that doesnt code for protein product
regulatory sequences
noncoding DNA that control gene expression
introns
sequences of noncoding DNA that interrupt genes
repetitive sequences
noncoding DNA that never gets transcribed
tandem repeats
back-to-back repetitive sequences
polymorphic regions
highly variable noncoding regions of DNA
recombinant DNA
combination of DNA from 2 sources into one molecule; occurs in nature due to viral transduction, bacterial transformation, conjugation, and moving transposons
uses of cloned genes
-making protein product
-replacing nonfunctioning gene using gene therapy
-to make multiple copies of gene for analysis
-to engineer bacteria to clean up environment
vector
cell that faciliates the carrying of a gene
gene cloning procedure
1. isolate gene of interest
2. insert gene into plasmid
3. insert plasmid into vector that carries plasmid after making bacteria competent
4. clone gene (plasmid and selected gene are reproduced along with the bacteria that reproduce themselves during binary fission)
5.identify bacteria that had gene and harvest it from the culture
competent
condition of a bacterium that is able to take up a plasmid
restriction enzymes
basic biotechnology tool that is extracted from bacteria and then used to cut DNA at specific recognition sequences (sites) and leave sticky ends so it can connect with other sticky ends on other restriction fragments; examples are EcoRI, BamHI, HindIII; used in gene cloning
gel electrophoresis
separates large molecules of DNA on the basis of their rate of movement through agarose gel in an electric field; smaller molecule=faster run; flows from cathode (-) to anode (+); commonly used to separate proteins and amino acids or to prepare for sequencing DNA
DNA probe
radioactively labeled single strand of DNA can be used in gel electrophoresis to identify the location of a specific sequence within the DNA
polymerase chain reaction
cell-free, automated technique by which a piece of DNA is amplified by placing in Taq polymerase along with nucleotides and primers
restriction fragment length polymorphisms
junk of human DNA showed restriction fragment pattern is different in every individual, resulting in this; example is DNA fingerprint
cDNA
DNA produced using fully processed mRNA from cells and the enzyme reverse transcriptase to make DNA transcripts from the fully processed RNA (since only a gene without introns must be inserted)