Chapter 8: Bacterial Genetics Flashcards
Microorganism that requires an organic growth factor
Auxotroph
Mechanism of horizontal gene transfer in which “naked” DNA is taken up by the recipient cell
Bacterial Transformation
Mechanism of horizontal gene transfer in which the donor cell physically contacts the recipient cell
Conjugation
Sequence of nucleotides in an organisms DNA
Genotype
Transfer of DNA from one organism to another by a process other than reproduction
Horizontal gene transfer
A change in the nucleotide sequence of a cell’s DNA that is passed on to daughter cells
Mutation
DNA molecule that replicates independent of the chromosome.
Plasmid
A microorganism that does not require any organic growth factors
Prototroph
Mechanism of horizontal gene transfer in which bacterial DNA is transferred inside a phage coat
Transduction
Segment of DNA that can move from one site to another in a cells genome
Transposon
Transfer of DNA from parent to offspring
Vertical gene transfer
Mutation changes existing nucleotide sequence, which is then passed to the offspring through _____
Vertical gene transfer
Bacteria are haploid or diploid
Haploid
Are spontaneous mutations passed on to offspring?
Yes
Mutation that corrects a defect caused by an earlier mutation
Reversion
A _____ is the most common type of mutation.
Base substitution
Mutation in which the wrong nucleotide has been incorporated
Base substitution
In a mutation if 1 base pait has been changed its called ______
Exp. AAC
TGG
Point mutation
Point mutation a type of base substitution happens during …
DNA synthesis
Base substitution mutation can lead to 3 different outcomes.
Synonymous (Still codes for correct amino acids) because the code is degenerative
Missense (Codes for the wrong protein)
Nonsense (Encodes a stop codon)
Base substitution are more common in aerobic or Anaerobic environments?
Why?
Aerobic
Reactive oxygen species, superoxide/ H²O², can oxidize the nucleobase of guanine causing it to be matched with adinine instead of cytosine
Mutation resulting from addition or subtraction of nucleotides not divisible by 3
Frameshift mutation
Segment of DNA that can move from one site to another in a cells genome
Transposon
Insertional inactivation occurs when…
A transposon “jumps” to a new spot in the genome
_____ are genetic changes that occur due to an influence outside of the cell, chemicals or radiation
Induced mutation
Compound that structurally resembles a nucleobase closely enough to be incorporated into a nucleotide in place of the natural nucleobase
Base analog
Base analogos lead to this type of mutation
Point mutations
Agents that insert between base pairs in a DNA double helix
Intercalating agents
Intercalating agents cause this type of mutation
Frameshift
UV light causes mutations how?
Errors during the repair process of covalent bonded thiamine
X-rays cause mutations how?
Single or double strand breaks, leading to deletions
Can insertional inactivation caused by transposons be repaired?
No
2 methods of repair in Nucleotide Incorporation and how they differ
Proof reading by DNA polymerase
Mismatch pairs by a protein after DNA polymerase
What role does methylation play in mismatch repair
It allows the protein to know which is the “new strand” and which is the template strand
A mechanism cells use to remove damaged nucleobases in DNA and then repair the region of damge
Base excision repair
What is a thymine dimer?
2 thymines covalently bonded together
3 mechanism organisms have to prevent UV damage
Photoreactivation: uses an enzyme that breaks the covlanet bond with visible light
Nucleotide excision repair: a specific enzyme recognizes the damage and removes it. Using DNA polymerase and ligase to repair it.
SOS repair
In spontaneous mutation Error in nucleotide incorporation can be fixed by these 2 processes
Proofreading by DNA polymerase
Mismatch pair
In spontaneous mutation Damage nucleobase in DNA can be fixed by?
Base excision repair
Glycosylase removes the damaged nucleobase. A short stretch of that strand is then degraded, and a DNA polymerase synthesizes a replacement
Base excision repair
In mutagen-induced Mutation a Chemical can lead to an error in NUCLEOTIDE INCORPORATION. How can this be fixed
Proofreading and mismatch repair
In mutagen-induced Mutation UV light can cause a thymine dimer.
How can this be fixed
3 methods
- Photoreactivation
- Nucleotide excision
- SOS repair
Mutations that grow under which the parent cell cannot are easy to isolate by…
Direct selection
Technique of selecting mutants by plating on a medium which favors the mutant but not the parent
Direct selection
Technique used for isolating and IDing organisms unable to grow on a medium which the parents do, often involves Replica Plating
Indirect selection
Isolates auxotrophic mutant from protrophic parent strand
Indirect selection
Using 2 plates with varying nutrient content to distinguish between auxotroph and protorphs
Replica plating
Method for increasing the proportion of auxotrophic mutants in a population by using penicillin to kill growing prototrophic cells
Penicillin enrichment
A test for carcinogens by measuring the ability of a substance to increase the mutation frequency in a bacterial strain
Ames test
Why are liver cells added to the Ames test?
The liver enzymes may convert chemicals not normally a carcogen into a carcogen
A cell that carries a DNA molecule derived from 2 different DNA molecules
Recombinant
Genes can be transferred from a donor to a recipient by three different mechanics
Bacterial transformation (naked DNA is taken up from the environment by a bacterial cell
Transduction: DNA is transferred from one bacterial cell to another by a phage
Conjugation DNA is transferred during cell-to-cell contact
What is a phage
A virus that infects a bacteria
A piece of DNA that contains an origin of replication and can potentially be replicated by a cell
Replicon
Process by which a cell replicates a stretch of DNA with a segment that has a similar nucleotide sequence
Homologous recombination
In horizontal gene transfer, a physiological condition in which bacterial cell is capable of taking up DNA
Competent
In bacterial transformation
Once a strand of DNA is inside the competent cell the strand of the donor DNA integrates into the recipients genome by _____the strand it will replace becomes degraded
Homologous recombination
Phages can transfer bacterial genes from a donor to a recipient via…
Transduction
In _____ a segment of DNA is carried from one bacterial cell to another via a phage releases its DNA which Breakdown the DNA, it reforms making more phages But some phages form with bacterial DNA instead and inject this DNA into other cells where it can become integrated
Generalized transduction
Bacterial phage progeny that contain part of a bacterial genome instead of phage DNA due to an error in packaging
Transducing particle
What is transferred during conjunction
Plasmids
Give examples of replicons
What isn’t a replicon
Plasmids, chromesomes, transposons (contain an origin point)
DNA fragment with out origin point
Type of Plasmids that carry genes for sex pills and can transfer copies of itself to other bacteria during conjunction
Conjugative plasmids
What is required for conjunction
Plasmid called the F factor
What connects the f+(donor) cell to the f-(recipient) in conjunction
Then it retracts and _____ forms allowing the plasmid transfer
Pillus
Conjugation bridge
These cells have the F plasmid in their chromesome allowing the chromesome to be transfered during conjunction
Hfr cells
An altered F plasmid that contains chromosomal fragments
Results from an incorrect excision of an F plasmid that was integrated into the chromosomes
F’ (F prime)
The total sum of genes encoded by the various strains of a given species
Pan-genome
DNA sequence found in all strains of a particular species
Core genome
This genome is present in more than 1 but not all stains of a species
Accessory genome
These genes are only found in 1 stain of a species
Unique genes
______ are significant contributors to genome variations, which move from one DNA molecule to another
Mobile Genetic Elements
Mobile Genetic Elements include: 4
Plasmids, transposons, genomic islands, phage DNA
Plasmids that encode resistance to one or more antimicrobial medications or heavy metals
R plasmids
Transposons intergrate into their new location by _________, a process that does not need similar nucleotide sequence
Non-homologous recombination
If a transposon inserts itself into a _______, it can be transferred into other cells
Conjugtive plasmid
Large segment of DNA acquired from another species through horizontal gene transfer.
Genomic Island
Stretches of DNA in a bacteria that code for virulence factors and appear to have come from other bacteria
Pathogenicity Islands
Latent form of temperate phage, the phage DNA has generally been inserted into the host’s chromosome
Prophage
Replicon that is independent of the chromesome and generally encodes only non-essential genetic information
Plasmid
Segment of DNA that directs its own movement to another location in chromosomal or plasmid DNA
Transposon
Large genomic segment in a cells genome that originally came from another species
Genomic Island
The genome of bacteria can change either through _____ or _______
Mutation / horizontal gene transfer
The gene into which the transposon jumps is __________
Insertionally activitied
Some chemicals modify nucleobases, altering their _________
Hydrogen binding properties
Intercalating agents result in this type of mutation
Frameshift
Base exclusion repair uses specific DNA _______ to remove damaged nucleobases in DNA
Glycosylases
For newly acquired DNA to replicate in a cell, it must be a ______ or integrate into the cell’s _____
Replicon / genome
F+ cells synthesize _____, encoded on an ______
F pilus / F plasmid
______ cells have the F plasmid integrated into the chromesome
Hfr cells
_______ allow bacterial cells to quickly distinguish and destroy invading DNA
Restriction-modification systems
_______ allow bacterial cells to destroy invading DNA that has been encountered previously
CRISPR systems
Mobile Genetic Elements include
plasmids, prophages, pathogenicity islands, restriction and modification systems, transposons
3 mechanics that bacteria use to adapt to changes in the environment
Which one doesn’t involve changes to the DNA originally had
Mutation
Gene transfer
Natural Selection ( No original DNA changr)
A Leaky mutation protein will have this level of functioning
Maybe Partial
The most serious type of point mutation according to the professor
Knockout
Transposon can cause Knockout mutations
T or F
T
Which drug in AIDS medication uses base analogues to cause the wrong base pair to form in new DNA
AZT
To repair base errors this enzyme Excises the wrong nucleotide in mismatch repair
Endonuclease
This type of repair for thymine dimers makes many mistakes
SOS repair
DNA mediated transformation occurs when a cell takes up naked DNA and usually occurs at the end of this phase
LOG growth
In bacterial transformation how many of the daughter cells contain the new DNA? 1 OR Both
1 because only a single strand of DNA is transferred
In artificial competence what is used to form a electroporation “pores forming in the cell wall to allow naked DNA to enter”
Electrical charge
In transduction an enzyme called Deoxyribonuclease does what
Cuts the bacterial chromesomes into peices
If plasmid is excised from main chromesome this cell is now called
F’
Plasmids are found in
Bacteria & Archea
Eukaryotes: Algea, Fungi, Protozoa
Are plasmids single or double stranded DNA
Double
Bacteria can conjugate with plants cells forming
GMOs
Virulence factors can be transferred by
Transduction, bacterial transformation, conjuction
Transposons occur in which cell types
Prokaryotic & eukaryotes
Generally Gene transfer occurs between organisms of the same species
Which 2 elements destroy foreign DNA
Restriction modification systems & deoxyribonuclease
Which type of cells have Restriction Enzymes
Prokaryotic
What is a Recognition Sequence?
Point in Prokaryotic cells where Restriction enzymes cleave Foreign DNA
Adding DNase to a mixture of donor and recipient cells will prevent gene transfer via
Bacterial transformation
The donor cell typically survives which DNA-transfer process?
Conjugation
Bacteria have 2 general mechanisms to adjust to new circumstances
Regulation of gene expression (existing genes turned “on” & “off”)
Genetic change: Existing Genetic make-up can change
Spontaneous mutation
Modified nucleobase in DNA
Action to repair
Action of glycosylase
Mutations that result from an Error in nucleotide incorporation are fixed by these 2 methods
Proofreading by DNA polymerase
Mismatched repair
Photoreactivation (light repair) is found only in
Bacteria
_____ isolates Auxotroph mutant from protrophic parent strand
Indirect selection
Bacterial defense against invading DNA
______ degrade foreign DNA
Restriction-modification systems
Crispr system
1st invasion Cas protien cuts DNA into fragments
Fragments inserted into CRISPR array; integrated DNA fragment is called ______
Subsequent invasion: transcription of CRISPR array generates _______ that direct DNA-cutting enzymes to invading DNA
Spacer
crRNA
Base excision repair uses this enzyme
Nucleotide excision repair uses this enzyme
Glycosylase
Endonuclease
________ are composed of three subunit molecules: a nucleobase, a five-carbon sugar (ribose or deoxyribose), and a phosphate group consisting of one to three phosphates.
Nucleotides
