Exam 3 (chapters 8, 9, 15, 20) Flashcards
Term for all genetic information in a cell:
genome
Term for segments of DNA that encode functional products, usually proteins:
genes
The ________ is a set of rules that determines how a nucleotide sequence is converted to an amino acid sequence of a protein.
genetic code
What are the four nitrogenous bases in DNA?
adenine, guanine, cytosine, thymine
What are the four nitrogenous bases in RNA?
adenine, cytosine, uracil, guanine
What two molecules make up chromosomes?
Each chromosome is made of protein and single molecule of DNA
How is the alteration of bacterial genes and gene expression important?
Helps understanding of cause of disease, how to prevent disease and treatment, can be manipulated for human benefit
List the chain of events described by central dogma:
DNA, mRNA, protein, function
Term for genetic makeup of an organism:
genotype
Term for expression of the genes (physical appearance of the organism in response to the genes expressed):
phenotype
Bacteria usually have what type of chromosome…made of ____ and _____?
single circular chromosome; single circular molecule of DNA; proteins
_____ are structures containing DNA that physically carry hereditary information.
chromosomes
What forms the basic structural unit of DNA?
nucleotides
What is a nucleotide made of?
nitrogenous base, pentose sugar, phosphate
What determines the genetic code?
the order of the nitrogen containing bases (contain the genetic instructions of the organism)
DNA forms a ______. The backbone consists of_____.
double helix; dexoxyribose-phosphate
Two strands of nucleotides are held together by ____ between A-_ and C-_.
hydrogen bonds; T; G
During DNA _____ one strand serves as a template for the production of a second strand.
replication
What has to happen to the DNA strands for replication to occur?
the strands have to separate
T/F DNA replication is more than 99% accurate
True
Why is replication highly accurate?
because of the proofreading capability of DNA polymerase (able to fix mistakes and proofreads as each nucleotide is added)
Most bacterial DNA replication is _______.
bidirectional (because it is a circular chromosome)
When does DNA replication occur in the life of a cell?
before cell division
How do bacteria divide?
binary fission
What two processes are involved in gene expression?
transcription and translation
When the information stored in our DNA is converted into instructions for making proteins or other molecules, it is called:
gene expression
Term for the synthesis of a complementary mRNA strand from a DNA template:
transcription (DNA > RNA)
Transcription begins when _____ binds to the ____ promoter sequence on DNA.
RNA polymerase; promoter
Transcription proceeds in the __’ to __’ direction.
5;3
T/F only one of the two DNA strands is transcribed during transcription
True
Transcription stops when it reaches the _____ sequence on DNA.
terminator
Term for the process where mRNA is translated into the “language” of proteins:
translation (RNA > PROTEIN)
What does transcription produce?
mRNA
Where does transcription take place in bacteria?
cytoplasm (because prokaryotes lack a membrane bound nucleus)
Where does transcription take place in eukaryotes?
membrane bound nucleus
What are groups of three mRNA nucleotides that code for a particular amino acid?
codons
How many codons encode the 20 amino acids:
64
Type of RNA that is an integral part of ribosomes:
ribosomal RNA (rRNA)
Type of RNA that transports amino acids during protein synthesis:
transfer RNA (tRNA)
Type of RNA that carries coded information needed to make protein from DNA to ribosomes:
messenger RNA (mRNA)
What are the three types of RNA?
ribosomal, transfer, messenger
Components of ribonucleic acid:
single-stranded nucleotide, 5-carbon ribose sugar, uracil instead of thymine
What does the process of translation produce?
proteins
Protein synthesis is called ______.
translation
Where does translation take place in bacteria?
cytoplasm
Where does translation occur in eukaryotes?
outside the nucleus in the cytoplasm
The genetic code involves ______, meaning each amino acid is coded by several codons.
degeneracy
How many amino acids does a cell need to make all of its proteins?
20
How many codons are there in the genetic code?
64
How are amino acids joined?
peptide bonds
Translation of mRNA begins at the:
start codon (AUG)
Translation ends at:
nonsense codons (UAA, UAG, UGA)
T/F In bacteria, transcription and translation can happen simultaneously…is this true in eukaryotic cells?
True. But they cannot occur simultaneously in eukaryotic cells because transcription occurs in the membrane bound nucleus and translation occurs in the cytoplasm
Term for self-replicating circular pieces of DNA:
plasmids
What often codes for proteins that enhance the pathogenicity of a bacterium?
plasmids
_____ and ______ are genetic elements that exist outside of chromosomes:
plasmids; transposons
Can plasmids be replicated?
Yes, they can replicate independently
Can plasmids be passed on to the next generation of bacterial cells?
Yes: increases pathogenicity
What are the three types of plasmids?
conjugative, dissimilation, resistance factors (R factors)
What carries genes for sex pili and transfer of the plasmid?
conjugative plasmid (horizontal gene transfer)
What encodes enzymes for the catabolism of unusual compounds?
dissimilation plasmids
What encodes antibiotic resistance?
resistance factors (R factors)
How do bacteria reproduce?
binary fission
Three ways that bacteria create genetic variation:
transformation, conjugation, transduction
When genes are transferred from one bacterium to another as “naked” DNA:
transformation
What are the two ways transformation can occur?
Naturally and artificially (in lab)
How is natural transformation beneficial or not to bacteria?
less prevalent (few bacteria take up the DNA–only those that are competent). PROS: plasmids can be acquired this way, and increased antibiotic resistance.
How is artificial transformation in bacteria useful?
recombinant DNA technology
When plasmids are transferred from one bacterium to another–requires cell-to-cell contact via sex pili:
conjugation
Term for the donor cells that carry the plasmid:
F plasmid
Cells that contain the F factor on the chromosome:
Hfr cells
Transduction can transfer bacterial DNA from one cell to another via:
bacteriophage
Term for the use of microorganisms, cells, or cell components to make a product such as: food, antibiotics, enzymes, vitamins:
biotechnology
Term for the insertion or modification of genes to produce desired proteins:
recombinant DNA
What cuts specific sequences of DNA as a way to destroy bacteriophage DNA in bacterial cells?
restriction endonucleases
What carries new DNA to desired cells and must be able to self-replicate?
vectors
What can be used as vectors?
plasmids and viruses
What enzyme is used to splice a gene of interest into a vector?
DNA ligase
When the recombinant DNA plasmid can be introduced into a host organism, this is called:
transformation
Process of increasing small quantities (amplifying) of DNA for analysis:
Polymerase Chain Reaction (PCR)
Why would someone use PCR in the lab?
diagnostic tests for genetic disease and to detect pathogens
What are the requirements for PCR?
DNA template, primers, Taq polymerase, nucleotides, thermocycler
Term for the sample used for PCR testing:
DNA template
Short pieces of nucleic acid that help start the reaction during PCR testing:
primers
What is the enzyme used to synthesize the new copy of DNA (comes from a hot spring prokaryote called Thermus aquaticus):
Taq polymerase
More examples of PCR uses:
DNA fingerprinting, gene cloning, forensic science, medical diagnosis, microbial detection
Name some therapeutic application for recombinant DNA technology:
insulin production using human enzymes, subunit vaccines, gene therapy, gene slicing,
Term for understanding gene function via computer-assisted analysis:
bioinformatics
Term for the ability to cause disease:
pathogenicity
Term for the degree of pathogenicity
virulence
What is the preferred portal of entry?
GI and respiratory
This measures the virulence of a microbe based on infectious dose needed to cause illness in 50% of population:
ID50
This measures the potency of a toxin what is needed as a lethal dose to cause lethality in 50% of a sample population:
LD50
Almost all pathogens attach to host tissues in a process called ______.
adherence
The attachment between pathogen and host is accomplished by means of surface molecules on the pathogen called ____ or _____ that bind specifically to complementary surface receptors on the cells of certain host tissues.
adhesins; ligands
Where can adhesins be located?
glycocalyx, pili, fimbriae, flagella
What are the ways a microbe can penetrate host defenses?
capsules, cell wall components, enzymes, antigenic variation, penetration into host, biofilms
How can microbes evade the immune system?
impairment of phagocytosis
What is a heat-resistant, acid-resistant, component found on the cell surface and fimbriae? It helps bacterium resist phagocytosis and mediates attachment of bacterium to epithelial cells of the host.
M protein
What is a protein that allows attachment to host cells and facilitates the host cell’s intake of the bacterium (also resists phagocytosis)?
Opa
What resists digestion by phagocytosis?
mycolic acid
Name the exoenzymes (5):
coagulases, kinases, hyaluronidase, collagenase, IgA proteases
This is an exozyme that coagulates fibrinogen to form clots in the host that can protect the bacterium from phagocytosis:
coagulases
Example of a coagulase:
Staphylococci
This is an exozyme that digests fibrin clots the host uses to isolate the infection:
kinases
Example of kinase:
Streptococcus pyogenes
This is an exozyme that digests polysaccharides that hold cell together to help pathogen spread from the initial infection site (promotes circulation of the pathogen):
hylauronidase
Example of hyaluronidase:
streptococci, clostridia
This exozyme breaks down collagen to facilitate the spread of gas gangrene:
collagenase
This exozyme destroys IgA antibodies secreted by mucous membranes:
IgA proteases
Term for a pathogen’s ability to alter their surface antigens so that antibodies are rendered ineffective which allows them to evade the adaptive immune system:
antigenic variation
Proteins secreted by pathogens that bind iron more tightly than host cells thus robbing the host cell of major nutrients:
siderophores
Term for poisonous substances produced microorganisms (produce fever, cardiovascular problems, diarrhea, shock):
toxins
The ability of a microorganism to produce a toxin:
toxigenicity
The presence of toxin in the host’s blood:
toxemia
The presence of toxin without microbial growth:
intoxications (only a small amount of the organism is needed to make you sick)
What are two types of toxins?
exotoxins and endotoxins
(Endotoxin or Exotoxin) This type is very specific in its effect and causes disease-specific signs and symptoms; soluble in body fluids; proteins are secreted and produced by the bacteria.
Exotoxins
List examples of exotoxins:
A-B toxins, membrane-disrupting toxins, superantigens, genotoxins
Most exotoxins fall in this category. Contain an enzyme component (A–alters function of host cell) and a binding component (B–helps make contact with host cell):
A-B toxins
What type of exotoxin (broad category) lyse host cells by disrupting plasma membranes:
membrane-disrupting toxins
Examples of membrane-disrupting toxins:
leukocidins, hemolysins, streptolysins
What type of toxin (endo- or exotoxin) is part of the outer portion of the cell wall of gram-negative bacteria?
endotoxins
Endotoxin that is part of gram negative bacteria:
Lipid A
Do you all endotoxins cause the same signs and symptoms regardless of the species of microbe? What are those symptoms?
Yes; chills, fever, weakness, aches
What kinds of symptoms are unique to endotoxins?
activation of blood clotting
Term for visible effects of viral infection on a cell (changes the way the cell behaves):
cytopathic effects (CPE)
Name some cytopathic effects:
causing cell lysosomes to release enzymes, changing host cell function or inducing chromosomal changes, inducing antigenic changes on cell surface
What can cause disease but does not have a well-defined set of virulence factors (more nondescript)?
fungi
What type of microbe provokes an allergic response?
fungi
This type of microbe causes symptoms due to their waste products:
protozoa
How do protozoa avoid host defenses?
digesting cells and tissue fluids, growing in phagocytes, antigenic variation
How do helminths cause problems for a host?
use host tissue for growth, produce waste products, cause cellular damage such as lymphedema (roundworm)
What type of microbe produces a neurotoxin called saxitoxin?
algae
Selectively finding and destroying pathogens without damaging the host:
selective toxicity
Use of chemical to treat disease:
chemotherapy (any med. to help overcome disease)
A substance produced by a microbe that in small amounts INHIBITS another microbe:
antibiotic
Synthetic substances that interfere with the growth of microbes:
antimicrobial drugs
When did Fleming discover penicillin and when was it first used on humans?
1928 (discovered); 1940 (first clinical trials)
More than half of our antibiotics are produced by _____ species of bacteria that commonly inhabit soil.
Streptomyces
Drugs that affect a narrow range of microbial types:
narrow spectrum drug
Drug that affect a broad range of gram-positive or gram-negative bacteria–also can destroy the normal microbiota of the host–can also cause the normal microbiota to flourish and become opportunistic pathogens:
broad-spectrum antibiotics
Term for an overgrowth of normal microbiota that is resistant to antibiotics:
surperinfection
Are eukaryotic or prokaryotic pathogens harder to treat?
eukaryotic (due to their similarity to host cells
Name of test that tests the effectiveness of chemotherapeutic agents:
Kirby-Bauer (disk diffusion) test
MIC stands for:
Minimal inhibitory concentration
Test that determines lowest antibiotic concentration preventing bacterial growth:
E test (determines minimal inhibitory concentration)
These cells have genetic characteristics allowing for their survival when exposed to an antibiotic:
Persister cells
Bacteria that are resistant to large numbers of antibiotics:
Superbugs
Five mechanisms of resistance:
- Enzymatic destruction or inactivation of drug 2. Prevention of penetration to the target site 3. Alteration of drug’s target site 4. Rapid efflux of antibiotic 5. Variation of these/combination of mechanisms
When the effect of two drugs together is greater than using one, it is called:
Synergism
When the effect of two drugs is less than the effect of either one, it is called:
Antagonism
Five actions of anti microbial drugs:
- Inhibiting cell wall synthesis 2. Inhibiting protein synthesis 3. Injuring plasma membrane 4. Inhibiting nucleic acid synthesis 5. Inhibiting the synthesis of essential metabolites
