Microbiology 303 Exam test quizzes
and answers graded A+
What are the parts of a plasmid? - ANS✅✅Circular double-stranded DNA
--Ori—origin of replication
--Amp—antibiotic resistance gene
--Restriction enzyme sites
Range in size from 2 kb to 1,000 kb
Encode accessory functions that are not essential for survival under most conditions
What is the difference between a plasmid and chromosome? - ANS✅✅Chromosomes: carries
essential genes
--Copy # varies
· Haploid—one copy
· Diploid—two copies
· Polyploid—many copies
--Usually circular
--1-12 Mb
Plasmids: carries non-essential genes
--Copy # varies: 1-100s of copies
--Can have different plasmids per cell
**Genomes can vary a lot!
How do plasmids maintain themselves in a host cell? How do they replicate? - ANS✅✅Replication:
Can direct their own replication
--Uses host machinery to copy
--Plasmid-encoded proteins (Rep protein) co-opt the cell's replication proteins
,--Need ori of replication
--Selfish for DNA
Segregation:
Have to make sure each daughter cell gets a plasmid
For-low copy plasmid
--Replication is coordinated with chromosome replication
For-high copy plasmid
--Random partitioning occurs
What is toxin-antitoxin system? - ANS✅✅Toxin is more stable
If plasmid is lost, antitoxin is degraded
--Toxin will be then be able to attack its targets
· Toxin is now active
--Plasmids use to prevent their loss
Example targets for toxins
--DNA gyrase
--mRNA
--Translation
--Peptidoglycan synthesis
How do genomes change? - ANS✅✅1. Errors during DNA replication
--Varies per organism
2. Spontaneous chemical changes in bases
--E.g. germination of cytosine to produce uracil
3. DNA damage
--Agents (mutagens) that damage DNA
**All of these can cause mutations, and if the daughter cell inherits that change, it is a mutant
, **Causes Evolution to occur
With a given change in a genotype, what mutation might have caused the change? - ANS✅✅1.
Errors during DNA replication
--Varies per organism
2. Spontaneous chemical changes in bases
--E.g. germination of cytosine to produce uracil
3. DNA damage
--Agents (mutagens) that damage DNA
Mutagens:
--Base analogs: causes faulty base-pairing based upon analog chemical structure
--Chemicals reacting with DNA: can chase a single change in base pairs
--Radiation: causes pyrimidine dimer formation and cause the DNA chain to break
**All of these can cause mutations, and if the daughter cell inherits that change, it is a mutant
**Causes Evolution to occur
What are the 6 types of ways the cells can repair DNA damage? - ANS✅✅1. Photoreactivation
2. Nucleotide excision
3. Base excision
4. Methyl mismatch
5. Recombination
6. Translation bypass synthesis/SOS response
What is photoreactivation? - ANS✅✅Repairs: pyrimidine dimers
1. UV light will hit the DNA and will cause a pyrimidine dimer
2. Photolyase will be bind
--Uses light energy to undo damage and repair DNA
What is nucleotide excision repair? - ANS✅✅Repairs: replication errors
and answers graded A+
What are the parts of a plasmid? - ANS✅✅Circular double-stranded DNA
--Ori—origin of replication
--Amp—antibiotic resistance gene
--Restriction enzyme sites
Range in size from 2 kb to 1,000 kb
Encode accessory functions that are not essential for survival under most conditions
What is the difference between a plasmid and chromosome? - ANS✅✅Chromosomes: carries
essential genes
--Copy # varies
· Haploid—one copy
· Diploid—two copies
· Polyploid—many copies
--Usually circular
--1-12 Mb
Plasmids: carries non-essential genes
--Copy # varies: 1-100s of copies
--Can have different plasmids per cell
**Genomes can vary a lot!
How do plasmids maintain themselves in a host cell? How do they replicate? - ANS✅✅Replication:
Can direct their own replication
--Uses host machinery to copy
--Plasmid-encoded proteins (Rep protein) co-opt the cell's replication proteins
,--Need ori of replication
--Selfish for DNA
Segregation:
Have to make sure each daughter cell gets a plasmid
For-low copy plasmid
--Replication is coordinated with chromosome replication
For-high copy plasmid
--Random partitioning occurs
What is toxin-antitoxin system? - ANS✅✅Toxin is more stable
If plasmid is lost, antitoxin is degraded
--Toxin will be then be able to attack its targets
· Toxin is now active
--Plasmids use to prevent their loss
Example targets for toxins
--DNA gyrase
--mRNA
--Translation
--Peptidoglycan synthesis
How do genomes change? - ANS✅✅1. Errors during DNA replication
--Varies per organism
2. Spontaneous chemical changes in bases
--E.g. germination of cytosine to produce uracil
3. DNA damage
--Agents (mutagens) that damage DNA
**All of these can cause mutations, and if the daughter cell inherits that change, it is a mutant
, **Causes Evolution to occur
With a given change in a genotype, what mutation might have caused the change? - ANS✅✅1.
Errors during DNA replication
--Varies per organism
2. Spontaneous chemical changes in bases
--E.g. germination of cytosine to produce uracil
3. DNA damage
--Agents (mutagens) that damage DNA
Mutagens:
--Base analogs: causes faulty base-pairing based upon analog chemical structure
--Chemicals reacting with DNA: can chase a single change in base pairs
--Radiation: causes pyrimidine dimer formation and cause the DNA chain to break
**All of these can cause mutations, and if the daughter cell inherits that change, it is a mutant
**Causes Evolution to occur
What are the 6 types of ways the cells can repair DNA damage? - ANS✅✅1. Photoreactivation
2. Nucleotide excision
3. Base excision
4. Methyl mismatch
5. Recombination
6. Translation bypass synthesis/SOS response
What is photoreactivation? - ANS✅✅Repairs: pyrimidine dimers
1. UV light will hit the DNA and will cause a pyrimidine dimer
2. Photolyase will be bind
--Uses light energy to undo damage and repair DNA
What is nucleotide excision repair? - ANS✅✅Repairs: replication errors
