VBS 2032 Exam 2 Questions and Correct
Answers
What are two general reasons bacteria change so rapidly?
1. Short generation times – some divide every ~20 minutes, so mutations spread
quickly.
2. Horizontal gene transfer (HGT) – bacteria can acquire genes from other bacteria.
What is a silent mutation?
DNA changes but the amino acid stays the same, so the protein is unaffected.
What is a missense mutation?
A base change causes one amino acid to change, which may alter the protein.
What is a nonsense mutation?
A mutation creates a stop codon, producing a shortened and usually nonfunctional
protein.
What do insertions and deletions cause?
Frameshift mutations that change the reading frame and usually make nonfunctional
proteins.
What is vertical transmission?
NA passed from parent cell to daughter cell during binary fission.
What is horizontal transmission?
DNA transferred between bacteria that are not parent and offspring.
What is transformation?
Uptake of free DNA from dead bacteria.
What is conjugation?
,DNA transfer through direct cell contact using a sex pilus.
What is transduction?
DNA transfer between bacteria by bacteriophages.
Why is genetic exchange beneficial for bacteria?
Rapid evolution
Spread of antibiotic resistance
Increased virulence
Greater adaptability
Why is genetic exchange important for humans?
It can lead to harder-to-treat infections and multidrug-resistant pathogens.
What two strains of Streptococcus pneumoniae did Griffith study?
Smooth (virulent, capsule) and Rough (nonvirulent, no capsule).
What happened when heat-killed smooth bacteria were mixed with live rough
bacteria?
The mice died and live smooth bacteria were recovered.
What did Griffith's experiment demonstrate?
Transformation — rough bacteria took up DNA from dead smooth bacteria.
What is a plasmid?
A small circular DNA molecule separate from the bacterial chromosome.
Where are plasmids found?
In the cytoplasm of bacteria.
What kinds of genes do plasmids often carry?
,Antibiotic resistance (R plasmids)
Virulence factors
Toxin genes
Metabolic genes
How can normal microbiota contribute to antibiotic resistance?
They can carry resistance plasmids and transfer them to pathogenic bacteria.
What is photoreactivation?
A light-dependent repair process where enzymes break thymine dimers using light
energy.
What is excision repair?
Damaged DNA is removed and DNA polymerase replaces it with the correct sequence.
What is a transposon?
A segment of DNA that can move within the genome.
Why are transposons significant?
They often carry antibiotic resistance genes and can move them onto plasmids.
What happens in the lytic cycle?
The phage replicates immediately and lyses (kills) the host cell.
What happens in the lysogenic cycle?
Phage DNA integrates into the bacterial chromosome and remains dormant as a
prophage.
Which gene transfer method involves phages?
Transduction
What is lysogeny?
, Integration of phage DNA into the bacterial chromosome.
How does the restriction-modification system protect bacteria?
Bacteria methylate their own DNA and restriction enzymes cut unmethylated foreign
DNA.
What is the CRISPR-Cas system?
A bacterial immune system that stores phage DNA and uses it to recognize and cut the
same phage during future infections.
Why does the species concept not work well for bacteria?
Because horizontal gene transfer causes huge genetic diversity within a species.
What is the core genome?
Genes shared by all strains of a species that perform essential functions.
What is the pangenome?
The total set of genes found across all strains, including accessory genes.
How was CRISPR used to treat sickle cell anemia?
Bone marrow cells were removed, edited to produce functional hemoglobin, and
transplanted back into the patient.
How is CRISPR used in biomedical research?
Gene editing
Gene knockouts
Disease modeling
Studying gene function
Developing gene therapies
How does MSA select for species of Staphylococcus?
Answers
What are two general reasons bacteria change so rapidly?
1. Short generation times – some divide every ~20 minutes, so mutations spread
quickly.
2. Horizontal gene transfer (HGT) – bacteria can acquire genes from other bacteria.
What is a silent mutation?
DNA changes but the amino acid stays the same, so the protein is unaffected.
What is a missense mutation?
A base change causes one amino acid to change, which may alter the protein.
What is a nonsense mutation?
A mutation creates a stop codon, producing a shortened and usually nonfunctional
protein.
What do insertions and deletions cause?
Frameshift mutations that change the reading frame and usually make nonfunctional
proteins.
What is vertical transmission?
NA passed from parent cell to daughter cell during binary fission.
What is horizontal transmission?
DNA transferred between bacteria that are not parent and offspring.
What is transformation?
Uptake of free DNA from dead bacteria.
What is conjugation?
,DNA transfer through direct cell contact using a sex pilus.
What is transduction?
DNA transfer between bacteria by bacteriophages.
Why is genetic exchange beneficial for bacteria?
Rapid evolution
Spread of antibiotic resistance
Increased virulence
Greater adaptability
Why is genetic exchange important for humans?
It can lead to harder-to-treat infections and multidrug-resistant pathogens.
What two strains of Streptococcus pneumoniae did Griffith study?
Smooth (virulent, capsule) and Rough (nonvirulent, no capsule).
What happened when heat-killed smooth bacteria were mixed with live rough
bacteria?
The mice died and live smooth bacteria were recovered.
What did Griffith's experiment demonstrate?
Transformation — rough bacteria took up DNA from dead smooth bacteria.
What is a plasmid?
A small circular DNA molecule separate from the bacterial chromosome.
Where are plasmids found?
In the cytoplasm of bacteria.
What kinds of genes do plasmids often carry?
,Antibiotic resistance (R plasmids)
Virulence factors
Toxin genes
Metabolic genes
How can normal microbiota contribute to antibiotic resistance?
They can carry resistance plasmids and transfer them to pathogenic bacteria.
What is photoreactivation?
A light-dependent repair process where enzymes break thymine dimers using light
energy.
What is excision repair?
Damaged DNA is removed and DNA polymerase replaces it with the correct sequence.
What is a transposon?
A segment of DNA that can move within the genome.
Why are transposons significant?
They often carry antibiotic resistance genes and can move them onto plasmids.
What happens in the lytic cycle?
The phage replicates immediately and lyses (kills) the host cell.
What happens in the lysogenic cycle?
Phage DNA integrates into the bacterial chromosome and remains dormant as a
prophage.
Which gene transfer method involves phages?
Transduction
What is lysogeny?
, Integration of phage DNA into the bacterial chromosome.
How does the restriction-modification system protect bacteria?
Bacteria methylate their own DNA and restriction enzymes cut unmethylated foreign
DNA.
What is the CRISPR-Cas system?
A bacterial immune system that stores phage DNA and uses it to recognize and cut the
same phage during future infections.
Why does the species concept not work well for bacteria?
Because horizontal gene transfer causes huge genetic diversity within a species.
What is the core genome?
Genes shared by all strains of a species that perform essential functions.
What is the pangenome?
The total set of genes found across all strains, including accessory genes.
How was CRISPR used to treat sickle cell anemia?
Bone marrow cells were removed, edited to produce functional hemoglobin, and
transplanted back into the patient.
How is CRISPR used in biomedical research?
Gene editing
Gene knockouts
Disease modeling
Studying gene function
Developing gene therapies
How does MSA select for species of Staphylococcus?
