Microbiology Chapter 6, 7, 9, 10
Paul Ehrlich
"magic bullets" - arsenic compounds that killed microbes - discovered the concept of selective toxicity
surfactants
"surface active" chemicals --> reduce surface tension of solvents soaps and detergents --> soaps have hydrophilic and hydrophobic ends --> detergents are positively charged organic surfactants quaternary ammonium compounds (quats) --> low-level disinfectants --> disrupt cellular membranes --> ideal for many medical and industrial applications --> not effective against non-enveloped viruses, mycobacteria or endospores
drugs
chemicals that affect the physiology in any manner
desiccation
(drying) - inhibits growth due to removal of water
lyophilization
(freeze-drying) - used for long term preservation of microbial cultures --> prevents formation of damaging ice crystals
DNA repair
- cells have numerous methods for repairing damaged DNA 3 categories 1. direct repair 2. single-strand repair 3. error-prone repair
ultrahigh-temp sterilization (pasteurization)
- 140C for 1 to 3 seconds, then rapid cooling - treated liquids can be stored at room temp for months (dairy creamer)
mutation
- change in the nucleotide base sequence of a genome - rare event - rarely leads to a protein that improves ability of organism to survive - almost always deleterious
disruption of cytoplasmic membranes (2)
- Azoles - allylamines - Polymyxin - Pyrazinamide - Praziquantel - Ivermectin
eukaryotic genomes - extranuclear chromosomes of eukaryotes
- DNA molecules of mitochondria and chloroplasts --> resemble chromosomes of prokaryotes --> only code for about 5% of RNA and proteins - some fungi and protozoa cay plasmids
central dogma of genetics
- DNA transcribed to RNA - RNA translated to form polypeptides
inhibition of cell wall synthesis
- Penicillins (discovered naturally) - Carbapenems - Cephalosporins - Monobactams (drugs that act to prevent cross linking)
Gramicidin, Polyenes
- Polyenes (Nystatin & Amphotericin B) attach to ergosterol in fungal membranes - Humans somewhat susceptible because cholesterol similar to ergosterol - Bacteria lack sterols; not susceptible
differences between RNA polymerase and DNA polymerase
- RNA polymerase unwinds and opens DNA by itself, no helicase required - does not need a primer - transcribes only 1 of the DNA strands - slower than DNA polymerase lll - incorporates ribonucleotides instead of deoxyribonucleotides - uracil nucleotides reincorporated instead of thymine nucleotides - proofreading function is less efficient
initiation of transcription
- RNA polymerases are enzymes that synthesize RNA - these enzymes bind to nucleotide sequences called promoters near beginning of genome - in bacteria, a polypeptide subunit of RNA polymerase called the sigma factor is necessary for recognition of promoter - primate transcribes RNA primer, and RNA polymerase transcribes mRNA, rRNA, and tRNA
transcriptional differences in eukaryotes
- RNA transcription occurs in nucleus (instead of cytosol) - transcription occurs in mitochondria and chloroplasts - RNA polymerases: mRNA, rRNA, tRNA - numerous transcription & elongation factors - mRNA processed before translation --> capping --> polyadenylation --> splicing
transfer RNA
- a sequence of 75 ribonuleotides - clover leaf structure with 3 main hairpin loops - transfers the correct AA to a ribosome during polypeptide synthesis - has an anticodon triplet in it bottom loop and an accept stem for a specific AA at its 3' end - Wobble hypothesis
chemical methods of microbial control
- affect microbes cells walls, cytoplasmic membranes, proteins, or DNA - effect varies with differing environmental conditions - often more effective against enveloped viruses and vegetative cells of bacteria, fungi, and protozoa
antimicrobial drugs
- antibiotic and semisynthetic and synthetic chemicals - typically used for treatment of disease - some used for antimicrobial control outside the body
enzymes
- antimicrobial agents act against microorganisms - human tears contain lysozyme --> digest peptidoglycan cell wall of bacteria - use enzymes to control microbes in the env't --> lysozyme used to reduce the # of bacteria in cheese - tears/saliva digest peptidoglycan --> Prionzyme can remove prions on medical instruments
Synthetics
- antimicrobials that are completely synthesized in a lab - pretty effective
initial process in bacterial DNA replication
- bacteria DNA replication begins at the origin - DNA helices unzips the DNA molecule forming a replication fork - DNA polymerase replicates DNA only 5' to 3' - because strand are antiparallel, new strands are synthesized differently
other characteristics of bacterial DNA replication
- bidirectional - gyrates and topoisomerases remove supercoils in DNA - DNA is methylated (generally adenine bases) --> control of gene expression --> initiation of DNA replication --> protection against viral infection --> repair of DNA
methods of microbial control using moist heat
- boiling - autoclaving - pasteurization - ultrahigh-temperature sterilization
action of antimicrobial agents alteration of cell walls and membranes
- cell wall maintains integrity of cell --> cells burst due to osmotic effects when damaged - cytoplasmic membrane contains cytoplasm and control passage of chemical into and out of cell --> cellular contents leak out when damaged - non enveloped viruses have greater tolerance of harsh conditions
Semisynthetics
- chemically altered antibiotics that are more effective, longer lasting, or easier to administer than naturally occurring ones - naturally occurring antibiotics are taken, functional groups modified to become more effective, easier to administer
chemostat cultures
- chemostat used to maintain a microbial population in a particular phase of growth - open system --> requires addition of fresh medium and removal of old medium - use din several industrial settings
aldehydes
- compounds containing terminal -CHO groups - cross-link functional groups (amino, hydroxyl, carboxyl) to denature proteins and inactivate nucleic acids - Glutaraldehyde disinfects and sterilizes --> 2% sol'n of glutaraldehyde disinfects and sterilizes - Formalin (37% aqueous sol'n of formaldehyde) used in embalming and disinfection of rooms and instruments --> is irritating and carcinogenic
refrigeration and freezing
- decrease microbial metabolism, growth, and reproduction --> chemical rxns occur at low temps --> liquid water not available - Psychrophillic microbes multiply in refrigerated foods - refrigeration halts growth of most pathogens - some microbes can multiply in refrigerated foods - slow freezing more effective than quick freezing due to ice crystals - organisms vary in susceptibility to freezing
Lincosamides Steptogramins Macrolide's
- drug that inhibit protein synthesis - bind to 50S subunit, would block the movement of ribosome by a codon - result in no movement of ribosome itself
Chloramphenicol
- drug that inhibits protein synthesis - act on larger ribosomal subunit (50S) - block peptide bond formation by blocking enzymatic activity that would lead to formation of peptide bond
Oxazolidinone's
- drug that inhibits protein synthesis - binds to mRNA cells, does not let 50S subunit attach, blocks formation of initiation complex
Tetracyclines
- drug that inhibits protein synthesis - block docking site of tRNA, the tRNA that comes in cannot bind and the movement of the ribosome stops completely
Aminoglycosides
- drug that inhibits protein synthesis - change shape of 30S ribosomal subunit, the mRNA is misread
Formiversen - antisense nucleic acid
- drug that inhibits protein synthesis - complementary strand to mRNA comes in and binds to mRNA - results in blocking of subunits - initiation complex itself is not formed
antimicrobial agents
- drugs that treat infections - anti fungal - antibacterial - antiprotozoal
Ionization Radiation
- e- beams, gamma rays, some X-rays - ejects e- from atoms to create ions - ions disrupt hydrogen bonding, oxidize double covalent bonds, and create hydroxyl radicals --> ions denature other molecules (DNA) - e- beams effective at killing microbes but do NOT penetrate well --> meat, spices, dental medical supplies, gloves, syringes - gamma rays penetrate well but require hours to kill microbes --> fresh fruit, veggies, spices, meat - X-ray require long time to kill microbes - not practical for microbial control
gene recombination and gene transfer
- exchange of nucleotide sequences often occurs between homologous sequences
types of plasmids
- fertility factors - resistance factors - bacteriocin factors - virulence plasmids
mechanisms of antimicrobial action
- fewer drugs to treat eukaryotic infections - antiviral drugs limited b/c they will take over the machinery of a eukaryotic cell
recombinants
- genetic recombination and transfer - cells with DNA molecules that contain new nucleotide sequences
osmotic pressure
- high concentration of salt or sugar in foods to inhibit growth - cells in HYPERTONIC solution of salt or sugar lose water - fungi have greater ability than bacteria to survive hypertonic environments
agents for the control of microbes should be
- inexpensive - fast-acting - stable during storage - capable of controlling microbial growth while being harmless to humans, animals, and objects
translation differences in eukaryotes
- initiation occurs when ribosomal subunit binds to 5' guanine cap - 1st amino acid is methionine rather than f-methionine - ribosome's can synthesize polypeptides into the cavity of the rough ER
translation differences in eukaryotes
- initiation occurs when ribosomal subunit binds to 5' guanine cap - first amino acid is methionine rather than f-mehionine - ribosomes can synthesize polypeptides into the cavity of the rough ER
alcohols
- intermedia-level disinfectants, not effective against spores - denature proteins and disrupt cytoplasmic membranes - more effective than soap in removing bacteria from hands - swabbing of skin with alcohol prior to injection removes most microbes - advantage is that they do not leave any residue - disadvantage --> may not contact microbes long enough to be effective
phenol and phenolics
- intermediate to low-level disinfectants - denature proteins and disrupt cell membranes - effective in presence of organic matter - remain active for prolonged time - commonly used in health care settings, labs, and homes - have disagreeable odor and possible side effects
halogens
- intermediate-level antimicrobial chemicals --> iodine, chlorine, bromine, and fluorine - damage enzymes by denaturation - effective against fungal sores and some bacterial endospores - widely used in numerous applications --> iodine tablets, iodophors, chlorine treatment, bleach, chloramines, and bromine disinfection
DNA replication
- key to replication is the complementary structure of the 2 strands - replication is semiconservative --> new DNA composed of one original and one daughter strand - anabolic polymerization processes require monomers and energy --> triphosphate deoxyribonucleotides serve both functions
development of resistant microbes
- little evidence that products containing antiseptic and disinfecting chemicals add to human or animal health - use of such products promotes development of resistant microbes
prokaryotic genomes - prokaryotic chromosomes
- main portion of DNA, along with proteins and RNA - prokaryotic cells are HAPLOID (single chromosome copy) - circular molecule of DNA in nucleoid (chromosome) - archael DNA wrapped around globular proteins called histones
gaseous agents
- microbicidal and sporicidal gases (ethylene oxide, propylene oxide, beta-propiolactone) used in closed chambers to sterilize items - denature proteins and DNA by cross-linking functional groups - used in hospitals and dental offices - disadvantages --> hazard to people --> highly explosive --> extremely poisonous --> potentially carcinogenic
direct methods not requiring incubation to measure growth
- microscopic counts - electronic counters --> coulter counters - counts cells as they interrupt an electrical current --> flow cytometry - detects changes in light transmission as cells pass a detector - serial dilution and viable counts - membrane filtration - most probable #
semisynthetic derivatives of beta-lactams
- more stable in acidic environments - more readily absorbed - less susceptible to deactivation - more active against more types of bacteria
beta - lactams
- most prominent in inhibition of cell wall synthesis - functional groups are beta-lactam rings - bind to enzymes that cross-link NAM subunits
frequency of mutations
- mutations are rare events --> otherwise organisms could not effective reproduce - mutagens increase the mutation rate by a factor of 10 to 1000 times - this change in gene frequency is the basis of evolution
Ivermectin
- parasitic drug - act against cytoplasmic membranes by changes the permeability
Praziquantel
- parasitic drug - act against cytoplasmic membranes by changes the permeability
oxidizing agents
- peroxides, ozone, and per acetic acid - kill by oxidation of microbial enzymes - high-level disinfectants and antiseptics that work by releasing oxygen radicals --> particularly effective against anaerobes - hydrogen peroxide can disinfect and sterilize surfaces --> not useful for treating open wounds due to catalase activity - ozone treatment of drinking water - per acetic acid is an effective sporicide used to sterilize equipment
methods to recognize mutants
- positive selection - negative (indirect) selection
autoclaving (moist heat)
- pressure applied to boiling water prevents steam from escaping - boiling temps increases as pressure increases - autoclave conditions: 121C, 15 psi, 15 minutes
inhibition of synthesis of bacterial walls
- prevent bacteria from increasing amount of peptidoglycan - have no effect on existing peptidoglycan layer - effective only for growing cells
inhibition of protein synthesis
- prokaryotic ribosomes are 70S (30S and 50S) - eukaryotic ribosomes are 80S (40S and 60S) - drugs can selectively target translation - mitochondria of animals and humans contain 70S ribosomes --> can be harmful
action of antimicrobial agents damage to proteins and nucleic acids
- protein function depends on 3-D shape --> extreme heat or certain chemicals denature proteins - chemicals, radiation, and heat can alter or destroy nucleic acids - produce fatal mutants - halt protein synthesis through action on RNA
preserving cultures
- refrigeration - stores for short periods of time - deep-freezing - stored for years - lyophilization - stores for decades
replication of eukaryotic DNA
- similar to bacterial replication - some differences --> uses 4 DNA polymerases --> 1000's of replication origins --> shorter Okazaki fragments: 100-400 nucleotides long --> plant and animal cells methylate only cytosine bases
insertion sequence (transposons and transposition)
- simplest transposons - have no more than 2 inverted repeats and a gene for transposase
Prokaryotes - Plasmids
- small molecules of DNA that replicate independently - not essential for normal metabolism, growth, or reproduction
disruption of cytoplasmic membranes
- some drugs form channel through cytoplasmic membrane to damage its integrity
temp on microbial growth
- the colder (20C), the more time to die out - the warmer (45C) the less time to die out
genome
- the entire genetic complement of an organism - includes its genes and nucleotide sequences
thermal death time
- time to sterilize volume of liquid at set temp - decimal reduction time --> time required to destroy 90% of the microbes in a sample
indirect methods to measure growth
- turbidity - metabolic activity - dry weight
point mutations
- type of mutation - most common - one base pari is affected - substitutions and frameshift mutations
Frameshift mutations
- type of mutation - nucleotide triplets after he mutations are displaced -insertions and deletions
eukaryotic genomes - nuclear chromosome
- typically have more than one chromosome per cell - linear chromosomes within nucleus - diploid (2 chromosome copies)
pasteurization (moist heat)
- used for milk, ice cream, yogurt, and fruit juices - NOT sterilization --> heat tolerant microbes survive - pasteurization of milk --> batch method --> flash pasteurization --> ultrahigh-temp pasteurization
dry heat
- used or materials that cannot be sterilized with moist heat - denatures proteins and oxidizes metabolic and structural chemicals - 171C for 1 hr or 160C for 2 hrs for baking glassware - incineration is ultimate means of sterilization
moist heat
- used to disinfect, sanitize, sterilize, and pasteurize - denatures proteins and destroys cytoplasmic membranes - most effective than dry heat
Non ionizing Radiation
- wavelengths greater than 1 nm - excites e-, causing them to make new covalent bonds --> affects 3D structure of proteins and nucleic acids - UV light causes pyrimidine dimers in DNA - UV light does not penetrate well - suitable for disinfecting air, transparent funds, and surfaces of objects
boiling (moist heat)
-kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses - boiling time is critical --> different elevations require different boiling times - endospores, protozoan cuts, and some viruses can survive boiling
6 types of RNA transcribed from DNA (events in transcription)
1. RNA primers: for DNA polymerase to use during DNA replication 2. mRNA: carry genetic info from chromosomes to ribosomes 3. rRNA: combine with ribosomal polypeptides to form ribosomes 4. tRNA: deliver correct sequence of amino acids to ribosomes based on nucleotide sequence in mRNA 5. regulatory RNA molecules: interact with DNA to control gene expression 6. Ribozymes
the greatest # of organisms are derived from
1. Streptomyces (bacterium) 2. Bacillus (bacterium) 3. Penicillium (fungi) 4. Acremonium (fungi)
culture media
1. defined 2. complex 3. selective 4. differential 5. anaerobic 6. transport
relationship between pressure and temp
as temp increases, pressure increases
the initiation of translation in prokaryotes
1. the smaller the ribosomal unit attaches to mRNA at a ribosome-binding site (SD sequence) so as to position a start codon (AUG) at its P site 2. tRNA fmet attaches at the ribosome's P site. Energy from GTP is used to bind tRNA in place 3. the larger subunit attaches to form a complete initiation complex
Polyadenylation
100-250 adenine nucleotides are added to the 3' end
Gene function translation
3 stages of translation 1. initiation 2. elongation - require GTP 3. termination - require GTP all stages require additional protein factors
the elongation stages of translation
4. the tRNA delivers its specific AA to the A site. 5. Ribozyme forms a peptide bond between terminal AA and new AA 6. Ribosome moves one codon down the mRNA transferring each tRNA to the adjacent binding site (from P to E site and A to P site)
the elongation stages of translation 2
7. ribosome releases "empty" tRNA from the E site 8. Appropriate enzyme "recharges" the tRNA with another AA, cycle repeats, each time adding another AA
inhibition of cell wall synthesis - major class of drugs (3)
Anti fungal: - Echinocandins --> inhibits the enzyme that synthesizes gluten in the fungal cell walls
inhibition of cell wall synthesis - major class of drugs
Antibacterial: - Vancomycin and cylcoserine --> interfere with particular alanine-alanine cross bridges the link NAM subunits in many Gram-positives - Bacitracin --> blocks secretion of NAG and NAM from cytoplasm
Selman Waksman
Antibiotics - antimicrobial agents produced naturally by organisms
inhibition of cell wall synthesis - major class of drugs (2)
Antimycobacterial: - Isoniazid and ethambutol --> disrupt mycolic acid formation in mycobacterial species
participants in translation
Messenger RNA - Carries genetic information from a chromosome to ribosomes as triplets of RNA nucleotides (codons) that encode AA sequences - Differences in eukaryotic and prokaryotic RNA - Eukaryotic cells process pre-mRNA to make mRNA - One molecule of eukaryotic mRNA contains instructions for one polypeptide - Transcription and translation do not occur simultaneously in eukaryotic cells (transcription in nucleus and translation in cytoplasm)
Alexander Fleming (1929)
Penicillin released from Penicillium
factors affecting the efficacy of antimicrobial methods 2
RELATIVE SUSCEPTIBILITY OF MICROORGANISMS germicide classification -high-level germicides - kill all pathogens, including endospores - intermediate-level germicides - kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria - low-levi germicides - kill vegetative bacteria, fungi, protozoa, and some viruses
factors affecting the efficacy of antimicrobial methods
SITE TO BE TREATED - harsh chemicals and extreme het cannot be used on humans, animals, and fragile objects - method of microbial control based on site of medical procedure
capping
a modified guanine nucleotide is added to the 5' end of the mRNA
techniques developed for culturing microorganism
animal and cell culture - used when artificial media is inaccurate - viruses only grow w/in living cells low oxygen culture - CO2 incubators - candle jars
mechanisms of antimicrobial action - antibacterial drugs
antibacterial drugs constitute largest # and diversity of antimicrobial agents - because of cell wall
bisphenolic (triclosan)
benzene ring connected to an O connected to another benzene ring the 1st bonze ring has Cl and OH connected, and the 2nd had 2 Cl connected off different carbons
phenol shape
benzene ring with OH
phenolic shape (orthocresol)
benzene ring with OH and CH3 (methyl group)
Phosphonomycin
blocks the conversion of UDP-NAG to UDP-NAM by blocking pyruvyl transferase
complex transposons (transposons and transposition)
contain one or more genes not connect with transposition
effects of high temp (physical methods of microbial control)
denature proteins interfere with integrity of cytoplasmic membrane and cell wall disrupt structure and function of nucleic acids
Gerhard Domagk (1932)
discovered sulfanilamide
polymyxin
disrupts cytoplasmic membranes of Gram negatives --> toxic to human kidneys
Pyrazinamide
disrupts transport across cytoplasmic membrane of M. tuberculosis
chemotherapeutic drugs
drugs that act against disease
factors affecting the efficacy of antimicrobial methods 3
environmental conditions - temp and pH --> affect microbial death rates --> after the efficacy of antimicrobial methods - organic materials --> interfere with the penetration of heat, chemicals, and some forms of radiation --> may inactivate chemical disinfectants
termination
event in translation - release gators recognize stop codons --> modify ribosome to activate from the final tRNA --> severs the polypeptide from the final tRNA - ribosome released into subunits - polypeptides released at termination may function alone or together
generation time
generation time = (# min)(# of hrs) / # of generations - time required for a bacterial cell to grow and divide - dependent on chemical and physical conditions
relationship between genotype and phenotype
genotype: set of genes in the genome phenotype: physical features and functional traits of the organism
BSL - 4
handing microbes that cause severe or fatal disease
BSL - 1
handing pathogens that do not cause disease in healthy humans
BSL - 3
handling microbes in safety cabinets
BSL - 2
handling moderately hazard agents
heavy metals
heavy metal ions denature proteins --> arsenic, zinc, mercury, silver, copper --> combine with sulfur atoms in molecules of cysteine - low-level bacteriostatic and fungistatic agents - 1% silver nitrate to prevent blindness caused by Neisseria gonorrheae - thimerosal (mercury containing compound) - used to preserve vaccines (tetanus, flu, meningitis) - copper - controls algal growth by interfering with chlorophyll - have been superseded by less toxic alternatives
horizontal gene transfer among prokaryotes
horizontal gene transfer - donor cell contributes part of genome to recipient cell 3 types 1. transformation 2. transduction 3. bacterial conjugation
transcription
information in DNA is copied as RNA
Azoles
inhibit ergosterol synthesis
allylamines
inhibit ergosterol synthesis
Cycloserine
inhibit the activity of enzymes that add alanines to peptide side-chain
b-lactams (penicillins, cephalosporins, carbapenems, and monobactams)
inhibit the last step in PGN synthesis, the transpeptidation rxn that cross-links the peptide side-chains of the polysaccharide-peptidoglycan backbone
Vancomycin
inhibits transglycosylation (NAM is attached to NAG via glycosidic linkage) and transpeptidation
three steps of transcription
initiation elongation termination
genetic methods to measure growth
isolate DNA sequences of unculturable prokaryotes
thermal death point
lowest temp that kills all cells in broth in 10 minutes
Phenol coefficient
method for evaluating disinfectants and antiseptics - evaluates efficacy of disinfectants and antiseptics - compares an agents ability to control microbes to phenol - greater than 1.0 indicates agent is more effective than phenol - has been replaced by newer methods
kelsey-sykes capacity test
method for evaluating disinfectants and antiseptics - alternative assessment approved by the European Union - bacterial suspensions added to the chemical being tested - samples removed at predetermined times and incubated - lack of bacterial reproduction reveals minimum time required for the disinfectant to be effective
Use-Dilution Test
method for evaluating disinfectants and antiseptics - metal cylinders into broth cultures of bacteria - contaminated cylinder immersed into dilution of disinfectant - cylinders removed, washed, and placed into tube of medium - most effective agents entirely prevent growth at highest dilution - current standard test in the US - new standard procedure being developed
In-Use test
method for evaluating disinfectants and antiseptics - swabs taken from objects before and after application of disinfectant or antiseptic - swabs inoculated into growth medium and incubated - medium monitored for growth - accurate determination of proper strength and application procedure for each specific situation
identifying mutants, mutagens, a and carcinogens
mutants - descendants of a cell that does not repair a mutation wild types - cells normally found in nature
chemical mutagens
nucleotide analogs - 5' bromouracil --> disrupt DNA and RNA replication nucleotide-altering chemicals - HNO2 --> result in base-pair substitutions and missense mutations frameshift mutagens - acridine, ethidium bromide --> result on nonsense mutations
vertical gene transfer
organisms replicate their genomes and provide copies to descendants
translation
polypeptides synthesized from RNA
Bacitracin
prevents linkage of NAM and NAG and blocking their secretion from cytoplasm by binding the lipid carrier bactoprenol and preventing dephosphorylation
translation defintion
process in which ribosomes use genetic information of nucleotide sequences to synthesize polypeptides
ribosomes and ribosomal RNA
prokaryotic: 50S and 30S subunits form 70S eukaryotic: 60S and 40S subunits form 80S smaller subunit of ribosome shaped to accommodate 3 codons at one time has 3 tRNA-bindng sites - A site: accomodate tRNA delivering an AA - P site: holds a tRNA and the growing polypeptide - E-site: discharged tRNA's exit from this site
triphosphate ribonucleotides
provide the energy required for RNA synthesis
radiation
radiation - ionizing radiation --> X-rays, gamma rays- break covalent bonds of DNA backbone - non ionizing radiation --> UV light - from pyrimidine dimers
splicing
removing all the introns to make a functional mRNA containing only coding regions called exons
mechanisms of antimicrobial action - successful chemotherapy requires what
selective toxicity - needs to be more toxic to pathogen than pathogens host
genetics
study of inheritance and inheritable traits as expressed in an organisms genetic material
Quats
surfactants in which hydrogen atoms of an ammonium ion are replaced by other functional groups
leading strand
synthesized continuously
lagging strand
synthesized discontinuously
events in translation
termination - release factors recognize stop codons --> modify ribosome to activate ribozymes - ribosome dissociates into subunits - polypeptide releases at termination mat function alone or together
horizontal gene transfer among prokaryotes 3
transduction - generalize transduction --> transducer phage carries random DNA segment from donor to recipient - specialized transduction --> only certain donor DNA sequences are transferred
horizontal gene transfer among prokaryotes 2
transformation - one of the conclusive pieces of proof that DNA is genetic material - cells that makeup DNA are competent --> results from alterations in cell all and cytoplasmic membrane that allow DNA to enter cell
transposons and transposition
transposons - jumping genes --> segment of DNA that move from one location to another in the same or different molecule - result in a kind of frameshift insertion (transpositions) - transposons contain palindromic sequences at each end