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Chapter 8
Microbial Genetics
66
Microbiology
Undergraduate 2
03/06/2012

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Term
genetics
Definition
the science of heredity
Term
genome
Definition
all the genetic information in a cell
Term
chromosomes
Definition
structures that contain DNA, physically carry the hereditary information
Term
genes
Definition
segments of DNA that code for functional proteins
Term
base pairs
Definition
adenine to thymine (or Uracil), cytosine to guanine
Term
genetic code
Definition
the set of rules that determines how a nucleotide sequence is converted into the amino acid sequence of a protein
Term
genotype
Definition
the genetic makeup of an organism, represents the potential properties
Term
phenotype
Definition
actual, expressed properties
Term
genomics
Definition
sequencing and molecular characterization of genomes; can be used to identify strains of bacteria/viruses
Term
DNA replication
Definition
one double stranded parental strand divides into two identical double stranded daughter strands; is semi-conservative: each daughter strand contains one of the parent strands
Term
DNA adds in the _______ direction
Definition
3' to 5'
Term
Lagging strand
Definition
Okazaki fragments
Term
DNA Gyrase
Definition
relaxes supercoiling of DNA
Term
DNA helicase
Definition
unwinds DNA double strand
Term
DNA polymerase
Definition
synthesizes new DNA/proofreads and repairs DNA
Term
DNA primase
Definition
adds RNA primers for DNA polymerase
Term
RNA polymerase
Definition
transcribes DNA into mRNA
Term
DNA ligase
Definition
connects Okasaki fragments on the lagging strand
Term
DNA error
Definition
1 in 10 to the 10 bases
Term
Bacteria DNA replication
Definition
bidirectionally because of circular DNA, had origin of replication and termination
Term
Transcription
Definition
RNA polymerase binds to promotor site, translates DNA gene sequence until kicked off by the terminator
Term
Translation
Definition
occurs in ribosomal complex: large and small ribosome subunits +mRNA + tRNA with attached amino acids; mRNA code is read in triplets
Term
codon
Definition
triplet of amino acids
Term
Anticodons of tRNA are _______________ of mRNA
Definition
complementary
Term
sense codons
Definition
code for amino acids
Term
nonsense codons
Definition
don't code for amino acids
Term
There are ___ sense codons but only ____ amino acids
Definition
61; 20
Term
mRNA has introns spliced out before mRNA leads the nucleus. Eukaryotes or Prokaryotes
Definition
Eukaryotes.
Term
Lack of nucleus allows simultaneous transcription and translation. Eukaryotes or Prokaryotes
Definition
Prokaryotes.
Term
Regulatory Gene
Definition
before the operon; it encodes for the repressor protein molecule that switches inducible or repressible operons 'on' or 'off'
Term
operon
Definition
consists of the control region (promotor, and operator) and the structural gene region (part that is transcribed); the operator serve as a point of attachment for the repressor protein
Term
repression
Definition
a mechanism that inhibits gene expression/protein synthesis
Term
induction
Definition
a process that turns on the transcription of a gene
Term
inducible operon
Definition
can be switched from a default 'off' or 'on'. It uses a REPRESSOR protein to inhibit RNA polymerase transcription; the default position for the REGULATORY gene is 'on'. In the presence of an inducer molecule/protein or 'substrate' the repressor protein is inactivated and detaches from the operator sequence on the DNA. This allows transcription of the structural gene by RNA polymerase to occur.
Term
repressible operon
Definition
can be switched from a default 'on' to 'off'. Uses a corepressor molecule to activate the repressor protein. REGULATORY gene is still turned on but the protein product is inactive (not bound to the operator) until it is attached to the corepressor. The addition of the corepressor allows the repressor protein to bind to the operator, which inhibits transcription.
Term
positive regulation
Definition
though a gene may not be inhibited by a repressor attached to an operator region, RNA polymerase may still not bind without the help of another protein. This other protein is activated by another molecule in the environment, which activates it and allows it to bind to RNA polymerase. This aids RNA polymerase in binding to the promotor region so transcription can occur. Helps decrease energy loss on transcribing unneeded gene sequences.
Term
mutation
Definition
a change in the base sequence of DNA
Term
Base substitution (mutation)
Definition
most common type, a single base at one point in the DNA sequence is replaced with a different base; doesn't necessarily cause change in protein sequence because 61 codons code for only 20 amino acid types.
Term
Missense mutation
Definition
results in an amino acid change in the protein
Term
nonsense mutation
Definition
base substitution results in an earlier stop codon, results in a shorter protein
Term
frameshift mutation
Definition
one or few DNA nucleotide pairs are deleted/inserted; changing the 3 codon reading frame
Term
spontaneous mutation
Definition
occur spontaneously in teh absence of mutation-causing agents; occurs because occasional mistakes made during DNA replication (can be base substitution or frameshift
Term
mutagens
Definition
agents in the environment that directly or indirectly bring about mutations
Term
mutation rate
Definition
the probability that a gene will mutate when a cell divides, usually increased with the presence of mutagens
Term
identifying mutagens
Definition
can be tested/selected for based of phenotype
Term
positive (direct)
Definition
detects mutant cells by rejection of the non-mutants
Term
negative (indirect)
Definition
involves replica plating; mutant lose ability to synthesize something so it cn grow on certain mediums that none mutants can
Term
auxotroph
Definition
any mutant microbe having a nutritional requirement that is absent in the parent
Term
carcinogen
Definition
causes cancer; many mutagens are carcinogens
Term
Ames Test
Definition
tests for carcinogens; suspected carcinogens/mutagens identified if they cause a change in bacteria samples which allows them to grow when they wouldn't have otherwise; the more mutant colonies the stronger the carcinogen/mutagen
Term
Vertical Gene Transfer
Definition
information passed from one generation to teh next to the next, one cell divides into two identical daughter cells
Term
gene recombination
Definition
the exchange of genes between two DNA molecules to form new combinations of genes on a chromosome; involves chromosome crossing over
Term
horizontal gene transfer
Definition
genetic information transferred between cells for the same generation "recombination", often done through DNA plasmids, viruses, or sex pili; transfer involves 'donor' and 'recipient' cells
Term
transformation
Definition
genes are transferred from one bacterium to another as 'naked' DNA; *heat killed bacteria still have DNA that can be transferred to other bacteria
Ex. if mouse is injected with heat killed pathogen, the mouse will live. If mouse is injected with head killed pathogen and live non-pathogenic microbes, genetic transformation will occur turning the non-pathogens into pathogens and the mouse will die. (Griffith's experiment)
Term
Griffith's experiment
Definition
If mouse is injected with heat killed pathogen, the mouse will live. If mouse is injected with head killed pathogen and live non-pathogenic microbes, genetic transformation will occur turning the non-pathogens into pathogens and the mouse will die.
Term
conjugation
Definition
horizontal transfer also, occurs with plasmids; F factor-fertility, plasmids can be transferred from an F+ to F- cell via sex pili making two F+ cells;
Term
F+
Definition
plasmid present in cell
Term
F-
Definition
plasmid absent in cell
Term
Hfr
Definition
plasmid is incorporated into the cell's chromosomes
Term
transduction
Definition
3rd horizontal transfer; involves bacteriophages, bacteria DNA is transported from one cell to anotehr by the virus infection
Term
conjugative plasmids (special plasmids)
Definition
carries genes for sex pili/ for transfer of the plasmid between cells
Term
dissimilation plasmids (special plasmids)
Definition
code for unusual enzymes that aid in metabolism
Term
resistance factors (R factors)
Definition
plasmids that enable bacteria to be more resistance to certain drugs; can be resistance transfer factor or R-determinant
Term
RTF
Definition
resistant transfer factor (genes for plasmid conjugation/replication
Term
R-determinant
Definition
genes for more drug resistance
Term
transposons
Definition
small segments of DNA that move from one region of DNA to another; occurs in all organisms; occurs rarely; all carry the information for their own translocation
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