Questions and Answers
What was the main goal of the experiment involving Hfr donor and F- recipient cells?
Why was streptomycin used in the experiment?
What is the term for the horizontal gene transfer process that occurs naturally between bacteria?
What is the purpose of interrupting conjugation in the blender?
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What is the term for the phenomenon where multiple genes are transferred together from the donor to the recipient cell?
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Why were the surviving colonies tested for sensitivity to azide and ability to metabolize lactose or galactose?
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What is the primary reason why genetic transfer is used in bacterial genetic analysis instead of crosses?
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What is the correct order of events in transformation?
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Which of the following is an example of horizontal gene transfer?
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What is the term for the simultaneous transfer of two or more genes from a donor cell to a recipient cell?
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Which genetic transfer mechanism involves viruses?
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Why are loss-of-function mutations easier to identify in haploid bacteria?
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Which of the following is a result of horizontal gene transfer in bacteria?
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What term is used to describe the laboratory technique of introducing DNA into bacterial cells?
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What is the primary function of DNA uptake signal sequences in transformation?
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During transformation, what is formed when there are sequence differences between the two alleles?
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What is the main principle behind cotransformation?
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What is the purpose of treating cells with calcium chloride and a high temperature shock in artificial transformation?
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What is the term for the process in which an organism receives genes from another organism without being a direct offspring?
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What type of genes are often acquired through horizontal gene transfer?
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What is the main difference between artificial transformation and conjugation?
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What is the purpose of electroporation in artificial transformation?
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Study Notes
Genetic Transfer and Mapping in Bacteria
- Bacteria possess allelic differences that affect their cellular traits, but these differences are between different strains because bacteria are usually haploid.
- Haploidy makes it easier to identify loss-of-function mutations in bacteria than in eukaryotes, as recessive mutations are not masked by dominant genes.
- Bacteria reproduce asexually, so researchers rely on genetic transfer instead of crosses for genetic analysis.
Genetic Transfer Methods
- Three ways genetic material can be transferred from one bacterium to another:
- Conjugation: direct physical contact between donor and recipient cells, with DNA transfer from donor to recipient.
- Transduction: viruses incorporate bacterial chromosomal DNA fragments into newly made virus particles, which then transfer the DNA to recipient cells.
- Transformation: uptake of DNA fragments from the environment, which are then incorporated into the recipient cell's chromosome by recombination.
Transformation
- DNA uptake signal sequences are 9-10 bp long, repeated 1,000-2,000 times throughout the genome, and are used by some species for DNA uptake.
- Steps of transformation:
- Extracellular DNA is taken up by the cell.
- Heteroduplex formation due to sequence differences between alleles.
- Repair of heteroduplex by DNA repair enzymes.
- Cotransformation: used to map genes, with a high frequency for close genes and low or zero frequency for distant genes.
Artificial Transformation
- Laboratory method to introduce plasmids into cells:
- Calcium chloride and high-temperature shock make cells permeable to small DNA molecules.
- Electroporation uses an external electrical field to make cells permeable.
Medical Relevance
- Horizontal gene transfer: the process of receiving genes from another organism without being a direct offspring, which can occur within and between species.
- Examples of horizontal gene transfer include conjugation, transformation, and transduction.
- Genes acquired through horizontal gene transfer can confer antibiotic resistance.
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Description
This quiz is about the process of bacterial conjugation, focusing on the transfer of specific genes between cells. It involves the use of streptomycin to kill donor cells and understanding the characteristics of recipient cells.
