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Where is E. coli found?
Large human intestine
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Is E. coli beneficial or harmful to the human intestines?
beneficial
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What toxin does E. coli 0157 H7 have?
Shiga
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How did E. coli 0157 H7 acquire the toxin from Shigella?
When E. coli and Shigella came in contact with one another, E. coli picked up a Shigella plasmid and it made the E. coli harmful. It is now called E. coli 0157 because it acts like Shigella.
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What is genetics?
The study of what genes are, how they carry info, how info is expressed, and how genes are replicated.
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What is a gene?
A segment of DNA that encodes a functional product, usually is a protein.
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What is a chromosome?
Structure containing DNA that physically carries hereditary information; the chromosomes contain the genes.
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What is a genome?
It contains ALL the genetic information in a cell, not just the chromosomes.
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What is genomics?
The molecular study of genomes.
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What is a genotype?
The genes of an organism.
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What is phenotype?
Expression of the genes.
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How many chromosomes does a human have?
46
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How many chromosomes does a bacteria have?
1
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Parent cells have how many strands of DNA in the cell?
1
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E. coli can take 1 cell and turn it into 2 new cells in how long?
20 minutes.
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What is transcription?
Transcribing from DNA to RNA.
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What is a polymer of nucleotides composed of?
Adenine, Thymine, Cytosine, and Guanine.
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What is the double helix associated with?
Proteins.
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What is the "backbone" called?
Deoxyribose-phosphate
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What kind of bonds hold the strands together?
Hydrogen bonds.
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Where are the hydrogen held at?
They are held at AT(Adenine, Thymine) and CG(Cytosine, Guanine).
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Strands are...
antiparallel
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What is semi-conservative replication?
The old strand of replication never leaves; it will always be there.
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How is DNA copied?
- by DNA polymerase.
- -in the 5' --> 3' direction
- -initiated by an RNA primer
- -DNA polymerases can only add nucleotides to the 3' end
- -Leading strand is synthesized continuously
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What is the 5' --> 3' direction?
the way that the molecules are aligned (they are antiparallel).
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What is the DNA synthesis process?
One strand is continuous with no unattachments and the other will be discontinuous with Okazaski fragments.
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How often is the leading strand synthesized?
Continuously
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How often is the lagging strand synthesized?
Discontinuously
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How do bacteria replicate?
Binary Fission.
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What is transcription?
The process of creating an equivalent RNA copy of a sequence of DNA.
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DNA is transcribed to make...
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When does transcription begin?
Transcription begins when RNA polymerase binds to the promoter sequence on the DNA.
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What direction does transcription take?
5' --> 3' direction.
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When does transcription end?
- The termination sequence.
- -mRNA stops being made then is ready for translation.
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What makes RNA?
DNA makes RNA.
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In Eukaryote cells, where is DNA found?
In the nucleus.
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In a Prokaryotes, where is DNA found?
There is no nucleus in Prokaryotes, so the DNA is found throughout the cell.
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How is mRNA translated?
In codons (three nucleotides)
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What is the start codon for mRNA translation?
AUG
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Where does translation end?
- Nonsense codons
- - UAA, UAG, UGA
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What is protein made up of?
Amino acids.
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What is sickle cell anemia?
A result of one single amino acid that is missing.
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How many sense codons are there?
64
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64 sense codons on mRNA encode how many amino acids?
20
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The genetic code is...
degenerate or redundant
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What does tRNA carry?
The complementary anticodon
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Why is there redundency in the genetic code?
Because they are repeated sometimes.
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In eurkaryotes, mRNA has to leave what?
The nucleus.
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In prokaryotes, there is no nucleus so mRNA is...
Always available.
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Where do ribosomes attach?
mRNA
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What is the ribosome doing?
Making a protein.
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What is translation?
Taking nucleic acids and turning them into amino acids.
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What is an anticodon?
The complementary to what is on mRNA.
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What does tRNA do?
tRNA brings in the complementary (anticodon) that goes with the mRNA.
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The tRNA brings the matches to the mRNA to make?
A polypeptide chain.
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How are constitutive genes expressed?
- Fixed rate.
- -produce proteins that are always needed by cells.
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What is an operon?
Set of 3 genes that work together to start/stop.
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What are inducible genes?
They are genes turned on when they are needed.
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What are repressive genes?
They stop transcription.
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What does a catabolite repression do?
The pressence turns it off.
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How many genes are involved in lactose uptake in E. coli?
3
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What is a promoter?
Where mRNA polymerase initiates transcription.
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What is an operator?
Turns transcription on or off.
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What are structural genes?
They determine the protein structure.
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What are the promoter, operator, and structural genes called collectively?
The lac operator (for lactose).
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What is the process that turns on transcription in the presence of an inducer?
Induction.
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What is a substance that induces transcription of a gene called?
An inducer
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In E. coli, the presence of causes (indirectly) the rapid production of the enzyme B-galactosidase.
Lactose
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Lactose is considered to be?
An inducer
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What gene encodes a repressor protein that switches the inducible and repressible operons on and off?
The I gene.
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What kind of operon is a lac operon?
Inducible
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The lac operon is an inducible operon so when lactose is not present, what happens?
The repressor protein from the I gene binds to the operator site and therefore prevents transcription.
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(Induction)
If lactose isn't present in transcription, what won't happen?
Transcription won't happen.
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(Induction)
What does transcription need in order to happen?
Lactose
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(Repressible Operons)
Structural genes are transcribed until when?
Until they are turned off or repressed.
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(Repressible Operons)
When there are excess products present, the product will as a what?
A corepressor
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(Repressible Operons)
What does the corepressor bind to?
The repressor protein.
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(Repressible Operons)
What happens if there are lots of a substance present?
It can cause it to stop or prevent transcription.
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(Catabolite Repression)
Enzymes for metabolism are constitutive, this meaning what?
They are always present.
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(Catabolite Repression)
When lactose is no longer available, what happens?
Organisms are able to grow off of other carbon sources.
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(Catabolite Repression)
When glucose is no longer available, what will it go after?
Lactose
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(Catabolite Repression)
Glucose grows
Faster
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(Catabolite Repression)
Lactose grows
Slower
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What is mutation?
A change in the genetic material.
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What are the 3 different forms that mutation may be in?
Neutral, Beneficial, or Harmful.
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What is a mutagen?
An agent that causes mutations.
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What are 3 examples of mutagens?
UV light, Xrays, and Gamma rays.
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When do spontaneous mutations occur?
They occur in the presence of a mutagen.
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What could happen if DNA is exposed to Xrays?
It could cause a mutation such as cancer.
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Mutations occur in DNA and the mutation carries through to what process?
The translation process.
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What is a missense mutation?
A point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid, which can result in proteins being not functional.
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What is a nonsense mutation?
A point mutation in a sequence of DNA that results in a STOP codon.
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Which mutation (missense, nonsense, or frameshift) is the most serious?
Frameshift mutation.
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What is frameshift mutation?
Insertion or deletion of one or more nucleotide pairs.
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What is the spontaneous mutation rate?
1 in 10^9 replicated base pairs or 1 in 10^6 replicated genes.
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What is the mutagen rate?
10^-5 or 10^-3 per replicated gene.
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How many types of mutagens are there?
- 4
- -chemicals-organic
- -UV light
- -xrays
- -gamma rays- nuclear
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Which happens more frequently, mutagens or spontaneous mutation?
Mutagens.
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What may be structurally similar to nucleotides and will cause base pair mutations in the DNA?
Chemical Mutagens.
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What may cause small deletions or insertions in the DNA which can result in frameshift mutations?
Chemical mutagens.
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What is Aflotoxin?
- They are naturally occuring mycotoxins.
- -Aspergillus flavus
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Where can Aspergillus flavus be found?
In peanut butter. It is a mold.
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What is ionizing radiation?
Xrays and Gamma rays
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What does ionizing radiation cause?
It causes the formation of ions and free radicals that can react with nucleotides and the deoxyribose-phosphate backbone.
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What can fragment the DNA and cause breaks in the chromosomes?
Ionizing radiation.
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What can radiation kill?
It can kill organisms.
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What kind of radiation causes thymine dimers?
- UV radiation.
- -thymine dimers are 2 thymines together in DNA
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How can mutations or carcinogens be detected in a culture?
- 1. Ames test
- 2. Replica plating
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Which mutation detection procedure uses sterile velvet/felt as an inoculum?
Replica plating.
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How do bacteria and humans transfer genes?
Vertically
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When do vertical gene transfers occur?
They occur during reproduction between generations of cells.
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What are horizontal gene transfers?
The transfer of genes between cells of the same generation.
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What transfer is between 2 organisms?
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What does a horizontal gene transfer need?
A donor cell and a recipient cell.
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What does virulent mean?
Harmful
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What does avirulent mean?
Unharmful
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What is transformation?
Genes are transferred from one bacterium to another as "naked" DNA.
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What is bacterial conjugation?
The transfer of genetic material between bacterial cells by direct cell-to-cell contact between two cells.
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What is F+?
F+ is the donor cell that carries a plasmid(DNA).
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What is F-?
F- is the recipient cell that receives the plasmid(DNA).
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What happens to F- after it receives the plasmid?
It becomes F+.
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What does "F" stand for?
Fertility.
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What happens if "F factor" gets into DNA?
It will continue to replicate itself.
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What is transduction?
The process by which DNA is transferred from one bacterium to another by a virus.
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What is a bacteriophage?
A virus that infects bacteria.
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What is a conjugative plasmid?
Carries genes for sex pili and transfer of the plasmid.
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What are dissimilation plasmids?
- They encode enzymes for catabolism of unusual compounds.
- Example: Psuedomonas sp that can have plasmids able to produce enzymes to degrade toluene, camphor, and hydrocarbons. (used in bioremediation of oils)
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What are Psuedomonas good at resisting?
Resisting antibiotics.
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Can code for proteins that enhance pathogenicity.
Plasmids.
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What are R factors?
They are resistance factors. They encode antibiotic resistance.
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What is toxic shock?
Exfolliation of skin, causes circulatory problems.
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Exfoliative toxin of Staphylococcus aureus, neurotoxin of Clostridium tetani, are examples of?
pathogenic plasmid.
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What are transposons?
Segments of DNA that can move from one region of DNA to another.
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Transposons occur how often?
Rarely
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Transposons contain insertion sequences for?
Cutting and resealing DNA (transposase)
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