🧬 Genetic Mayhem
A single nucleotide substitution changes the amino acid encoded by a codon without creating a stop codon. What type of mutation occurred?
What is a missense mutation
A bacterium acquires naked DNA from its environment without direct contact with another bacterium or involvement of a virus. What process occurred?
what is transformation
A Gram-positive bacillus divides in a way that causes its outer wall to tear apart suddenly, often leaving daughter cells in a folded palisade arrangement. Name this method of division.
what is snapping division
A protozoan is currently motile, metabolically active and feeding. When conditions become unfavorable, it can enter a protected, low metabolism resting stage. Name the active stage AND resting stage.
Trophozoite; cyst.
Which scientist discovered that genetic information could move between bacterial cells through transformation?
Frederick Griffith
A mutation deletes a single nucleotide near the beginning of a coding sequence, changing most of the codons that follow it. What type of mutation is this?
What is a Frameshift mutation
A bacteriophage accidentally packages a random fragment of bacterial DNA and transfers it to another bacterium. What process occurred?
what is generalized transduction
You isolate an extremely small bacterium that lacks a cell wall but survives because sterols strengthen its cytoplasmic membrane. What group does it belong to?
what is mycoplasmas
A fungus grows as a mold in one environment but as a yeast in another. What characteristic does it display?
dimorphism
A bacterium divides, but its daughter cells remain attached in a side-by-side, picket-fence arrangement. What arrangement is this?
Palisades
Tryptophan levels become high inside a bacterium. Explain what happens to the trp repressor and ultimately to transcription of the trp operon.
Tryptophan activates the repressor → the active repressor binds the operator → transcription turns OFF.
A bacteriophage transfers only certain bacterial genes because those genes were located near the site where viral DNA had integrated into the chromosome. What process occurred?
what is specialized transduction
This group of Archaea consists of anaerobes that use compounds such as CO₂ and H₂ and ultimately produce methane.
what is methanogens
UV radiation causes neighboring pyrimidines in bacterial DNA to covalently bond, distorting the DNA and interfering with replication and transcription. What type of DNA damage has occurred?
pyrimidine dimers
A short RNA binds complementary mRNA, causing it to be sequestered or destroyed. Name either type from the study guide.
miRNA or siRNA
A bacterium has lactose available and very little glucose. Which regulatory molecule increases, what protein does it bind, and what is the ultimate effect on lac operon transcription?
cAMP increases → binds CAP → CAP promotes RNA polymerase binding → lac operon transcription increases.
An F⁺ bacterium successfully transfers a complete F plasmid to an F⁻ bacterium. What is the F status of the donor and recipient after conjugation?
F⁺ donor and F⁺ recipient.
Two anoxygenic phototrophic bacteria are compared. Organism A obtains electrons from organic compounds such as carbohydrates and organic acids. Organism B obtains electrons by oxidizing hydrogen sulfide. Classify A and B.
A = nonsulfur bacterium
B = sulfur bacterium
An unknown protozoan has one large mitochondrion containing a concentrated mass of DNA. What group and structure identify it?
Kinetoplastids; kinetoplast
A bacterium gains a mutation allowing it to survive under conditions that kill the wild type. What selection method can isolate it?
positive selection
A bacterium has lactose present and no glucose, but a mutation makes the lac repressor unable to release from the operator, even when lactose is present. What happens to lac operon transcription, and what happens to CAP/cAMP regulation?
The lac operon remains OFF. Because glucose is absent, cAMP levels rise, cAMP binds CAP, and CAP promotes RNA polymerase binding. However, the defective repressor remains bound and blocks transcription, so CAP/cAMP cannot overcome the repressor.
An F factor integrates into a bacterial chromosome. That bacterium then conjugates with an F⁻ cell, but the cells separate before the entire chromosome is transferred. The recipient obtains several donor chromosomal genes. Identify the donor AND predict the recipient's F status.
The donor is Hfr, and the recipient will usually remain F⁻, although it can acquire new donor genetic information.
A Mycoplasma and a Bacillus cell are exposed to a drug that blocks peptidoglycan synthesis. Which is directly affected, and why?
Bacillus, because it has a peptidoglycan cell wall; Mycoplasma lacks a cell wall.
Put these fungal sexual events in order: meiosis, dikaryon formation, karyogamy, haploid spore formation.
Dikaryon formation → karyogamy → meiosis → haploid spores
In an Ames test, His⁻ bacteria are placed on media without histidine. Chemical X produces many more colonies than the control. Why is histidine removed, and what does the result suggest?
His⁻ bacteria cannot normally grow without histidine, so growth selects for bacteria that changed. More colonies with Chemical X suggest it is mutagenic and potentially carcinogenic.