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