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77 Cards in this Set
- Front
- Back
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What are four differences between prokaryotes and eukaryotes?
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1) Prokaryotes lack nuclei and membrane-bound organelles
2) Prokaryotes have a single chromosome while eukaryotes have multiple linear chromosomes. 3) Prokaryotes have cell walls while most eukaryotes lack cell walls 4) Prokaryotes do not multiply by sexual reproduction, but many eukaryotes reproduce sexually. |
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Are bacteria prokaryotes or eukaryotes?
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Prokaryotes
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What does the bacterial genome consist of?
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1) Linear or circular double-stranded deoxyribonucleic acid chromosomes
2) Plasmids 3) Bacteriophage |
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What is a nucleoid?
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Another term for bacterial chromosomal DNA
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What does the chromosome contain?
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All the essential genes for bacterial survival.
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What is the ploidy of bacterial DNA?
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Haploid
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What does haploid mean?
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Haploid cells contain one set of chromosomes.
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What is the average genome size of bacterial DNA?
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0.876 - 8 million base pairs (Mbp)
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How does the size of the bacterial DNA compare to the average genome size of eukaryotes?
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Much smaller than eukaryotic DNA, which is typically 500 times greater than bacterial DNA.
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Where is DNA located in bacteria?
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Within the cytoplasm because bacteria lack membrane-bound nuclei.
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What is found in eukaryotic DNA but not in bacterial DNA?
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Histones and nucleosomes
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What are plasmids?
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Small extrachromosomal segments of circular DNA.
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What do plasmids contain?
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May contain transposons and genes and proteins that promote transfer of the plasmid to other cells.
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What are transposons?
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Mobile DNA sequences that can move from plasmid to plasmid and/or from bacteriophage DNA.
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What is the name for the special sequence of DNA that is required for replication in prokaryotic cells?
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Replication origin, also known as "ori"
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How many replication origins (ori) are present in bacterial DNA?
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One
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What is the name for the region of DNA that contain these sequences?
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Replicons
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What enzymes are important for adding DNA base pairs during replication?
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DNA polymerases
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In which direction do DNA polymerases work?
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Bidirectionally, but always 5' - 3'
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How do plasmids replicate?
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Independently of the main chromosome
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What are three distinct mechanisms by which DNA is transferred between bacteria?
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1) Conjugation
2) Transduction 3) Transformation |
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What is conjugation?
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Process where bacteria transfer genetic material from one cell to another by means of cell-to-cell contact.
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What structure assists in conjugation between bacteria?
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Sex pili.
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How do sex pili assist in conjugation?
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They are hair-like projections that bind donor and recipient cells, bringing them closer together.
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What genetic material is transferred during conugation?
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Conjugative plasmids
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What portion of the plasmid is transferred during conjugation?
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Only one strand of the double-stranded plasmid is transferred to the recipient cell.
The complementary plasmid strand is synthesized by the recipient cell. |
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What is the prototypic conjugative plasmid found in Escherichia coli?
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F, or fertility, plasmid
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What medically important genes are often contained within plasmids?
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Antibiotic resistance genes and structural genes for the pilus protein.
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What is the name for bacteria in which th F plasmid beccomes integrated into the bacterial chromosome?
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Hfr (high frequency of chromosomal recombinants)
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What is transduction?
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Process where viruses transfer genetic material from one bacteria to another by means of a bacteriophage without any cell-to-cell contact
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What is a bacteriophage?
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Virus that replicates within bacterial cells.
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What is the composition of a bacteriophage?
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Single or double-stranded nucleic acid (DNA or RNA) within a protective protein coat.
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What are five stages of bacteriophage replication?
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1) Phage attachment (adsorption)
2) Injection of phage DNA (penetration) 3) Synthesis of phage DNA or proteins 4) Assembly of new phage particles 5) Lysis of cell and release of new phage progeny. |
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What are two types of phage?
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Viruent and temperate
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What is the name of the virulent phage replication cycle?
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Lytic cycle
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What are the steps of the lytic cycle?
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1) Virulent phage infect cells
2) Replicate intracellularly 3) Lyse and kill host cells 4) Release new phage particles |
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What is the name of the temperate phage replication cycle?
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Lysogenic cycle
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What are the steps of the lysogenic cycle?
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1) Temperate phage infect cells
2) Phage genome integrates into the host chromosomal DNA 3) Remains silent and replicates as part of the host chromosome. |
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What is the name for a phage that is integrated within the host chromosome?
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Prophage
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What prevents expressoin of the phage once it has been integrated within the host chromosome?
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The phage encodes a repressor protein that prevents expression of other phage genes.
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What are two types of transduction?
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1) Generalized transductoin
2) Specialized transduction |
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What is generalized transduction?
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Process where phage enzymes cleave bacterial DNA into fragments which are randomly packaged in a phage protein coat and released during cell lysis.
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What is specialized transduction?
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Process where chromosomal bacterial genes closely upstream or downstream to the prophage insertion site are transferred because they are randomly excised and packaged into a phage protein coat and release during cell lysis.
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What type of phage is involved in specialized transduction?
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Temperate phage
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What is transformation?
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Process where transfer of genes occurs by cellular uptake of naked DNA fragments.
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What is the term for the ability of a recipient cell to take up naked DNA?
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Competency
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How does naked DNA enter a cell?
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It binds to the cell wall and is taken up intracellularly or passes through defects in the cell wall.
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How does naked DNA become integrated?
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One strand of the naked DNA binds to a region of sequence homology on the recipient chromosome, replacing the original complementary strand, while the second strand of naked DNA is destroyed by cell nucleases.
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What is a wild type organism?
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A standard to which genetic mutants are compared.
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What is a mutant?
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An organism that deviates from normal in some recognizable characteristic (phenotype)
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What is a mutation?
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A change in the base sequence of DNA (genotype).
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What is an unstable mutation?
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A mutation which frequently changes back to its original state.
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How are nucleotides classified?
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Purines: adenine, guanine have two rings
Pyrimidines: cytosine, thymine have one ring (CUT the PY) |
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What is a point mutation?
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A mutation that only affects one base pair.
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What are two types of point mutation?
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Transposition substitution
Transversion substitution |
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What is a transition substitution?
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A point mutation where a purine is substituted for a purine or a pyrimidine is substituted for a pyrimidine.
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What is a transversion substitution?
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A point mutation where a purine replaces a pyrimidine or vice-versa.
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What is an inversion mutation?
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A mutation where a string of base pairs are deleted and reinserted in teh same position, but in the opposite direction.
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What is a silent mutation?
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A mutation that alters base pairs, but not the specific amino acid they encode.
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What is a missense mutation?
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A mutation that alters base pairs, resulting in the replacement one amino acid residue for another.
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What is a nonsense mutation?
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A mutation resulting in a stop codon, prematurely terminating the elongation of a polypeptide chain.
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A frame-shift mutation?
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A mutation that changes the reading frame of the genetic code, resulting in a misreading of all downstream nucleotides and altering the encoded amino acids of the polypeptide chain, often resulting in early stop codons.
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What common properties are used to categorize mutants?
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Nutritional needs, temperature-sensitivity, capability to suppress mutations, and capability to regulate gene expression.
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What are seven classes of mutagenic agents?
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1) Base analogs (5-bromouracil)
2) Chemical modifiers (nitrous acid, hydroxylamine, alkylating agents) 3) Frame-shift mutagens (acridine) 4) Radiation (UV light, x-rays) 5) Mobile genetic elements (transposons) 6) Oxidizing agents (hydroxyl radicals, superoxide) 7) Intercalating agents (ethidium bromide, daunomycin) |
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What laboratory test can be used to detect mutagens?
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Ames test
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What is the Ames test?
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A laboratory test that allows investigators to identify mutagens by performing the following:
1) Potential mutagens are addd to strains of Salmonella that have been genetically modified to require histidine for growth. 2) these bacteria are plated on medium lacking histidine. 3) Bacteria that grow in the absence of histidine are presumed to have acquired a mutation allowing them to produce histidine. |
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How do bacteria demonstrage negative control for gene expression?
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Bacteria encode repressor proteins that bind to operator sites, preventing expression of dounstream genes
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What is an inducer?
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A protein or molecule that binds to and inhibits the repressor, allowing expressoin of downstream genes.
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What is an acitvator?
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A protein or molecule that binds to chromosomes, increasing gene expression
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What are G- cocci?
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Acinetobacter (oxidase -)
M. catarrhalis N. gonorrhoeae (glucose fermentation +) N. meningitidis (maltose fermentation +) |
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What are Zoonotic Rods?
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Brucella
Francisella tularensis Yersinia pestis Pasteurella multiocida Bartonella |
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What are Opportunistic Rods?
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Pseudomonas
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What are Respiratory Rods?
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Haemophilus influenzae
Legionella pneumophila Bordetella pertussis |
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What are Enteric Rods?
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Bacteroides
Campylobacter Enterobacter Escherichia Fusobacterium Helicobacter Klebsiella Prevotella Proteus Pseudomonas Salmonella Serratia Sigella Vibrio Yersinia |
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What are G+, Catalase +, Cocci?
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Staph. aureus
Staph. epidermidis Staph. saprophyticus |
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What are G+, Catalase - Cocci?
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Alpha hemolytic
1) Strep. pneumoniae 2) Strep. viridans Beta hemolytic 1) Strep. pyogenes 2) Strep. agalactiae Delta hemolytic 1) Peptostreptococcus 2) Enterococcus |
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What are G+ Rods
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Corynebacterium
Clostridium Bacillus Listeria Propionibacterium Lactobacillus Erysipelothrix |
