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Questions and Answers
What is the central dogma of molecular biology?
What is the central dogma of molecular biology?
DNA → RNA → Protein
Which of the following is NOT a common type of gene transfer in bacteria?
Which of the following is NOT a common type of gene transfer in bacteria?
The process of ______ is the decoding of mRNA into a sequence of amino acids to generate a protein.
The process of ______ is the decoding of mRNA into a sequence of amino acids to generate a protein.
translation
What is the function of transposase?
What is the function of transposase?
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A silent mutation results in a change in the amino acid sequence of a protein.
A silent mutation results in a change in the amino acid sequence of a protein.
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Which of the following is NOT a mechanism of horizontal gene transfer in bacteria?
Which of the following is NOT a mechanism of horizontal gene transfer in bacteria?
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What is the name of the genetic element that allows for the transfer of genetic material during conjugation?
What is the name of the genetic element that allows for the transfer of genetic material during conjugation?
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Match the following types of gene transfer with their descriptions:
Match the following types of gene transfer with their descriptions:
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What is the term for a bacterial cell that can take up donor DNA, often due to alterations in its cell wall?
What is the term for a bacterial cell that can take up donor DNA, often due to alterations in its cell wall?
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Which of the following is a common application of plasmids in genetic engineering?
Which of the following is a common application of plasmids in genetic engineering?
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Which of the following is NOT an example of an inducible operon?
Which of the following is NOT an example of an inducible operon?
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What is the term for the process of altering gene expression by methylation of DNA?
What is the term for the process of altering gene expression by methylation of DNA?
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All mutations are harmful to the survival of an organism.
All mutations are harmful to the survival of an organism.
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What is the term for a mutation that results in a premature stop codon in the mRNA?
What is the term for a mutation that results in a premature stop codon in the mRNA?
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Which of the following is an example of a nucleoside analog that can act as a mutagen?
Which of the following is an example of a nucleoside analog that can act as a mutagen?
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What are the most common types of mutations that occur as a result of mutagens?
What are the most common types of mutations that occur as a result of mutagens?
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The Ames test is a rapid and relatively inexpensive screening method for identifying potential carcinogens.
The Ames test is a rapid and relatively inexpensive screening method for identifying potential carcinogens.
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What is the main outcome of genetic recombination?
What is the main outcome of genetic recombination?
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Which of the following bacterial gene transfer mechanisms is NOT a form of horizontal gene transfer?
Which of the following bacterial gene transfer mechanisms is NOT a form of horizontal gene transfer?
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Transposons can only move within a single chromosome.
Transposons can only move within a single chromosome.
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What is the term for a bacterial cell that has acquired a new genetic trait, often due to the integration of DNA from another source?
What is the term for a bacterial cell that has acquired a new genetic trait, often due to the integration of DNA from another source?
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During transformation, the process of ______ facilitates the exchange of DNA strands between the recipient and donor DNA.
During transformation, the process of ______ facilitates the exchange of DNA strands between the recipient and donor DNA.
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What is the name of the process that involves the transfer of genetic material from dead bacteria to live bacteria?
What is the name of the process that involves the transfer of genetic material from dead bacteria to live bacteria?
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R factors are plasmids that typically carry genes for antibiotic resistance.
R factors are plasmids that typically carry genes for antibiotic resistance.
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What is the main function of the enzyme transposase?
What is the main function of the enzyme transposase?
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What is the term for the transfer of genetic material from one organism to another without the involvement of reproduction or offspring?
What is the term for the transfer of genetic material from one organism to another without the involvement of reproduction or offspring?
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Specialized transduction involves the transfer of a specific set of genes from a donor cell to a recipient cell.
Specialized transduction involves the transfer of a specific set of genes from a donor cell to a recipient cell.
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Which of the following is NOT a key factor contributing to bacterial evolution?
Which of the following is NOT a key factor contributing to bacterial evolution?
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What is the name given to the process where genes are transferred from one bacterium to another as 'naked' DNA in solution?
What is the name given to the process where genes are transferred from one bacterium to another as 'naked' DNA in solution?
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Antibiotic resistance genes are often found on plasmids, particularly R factors.
Antibiotic resistance genes are often found on plasmids, particularly R factors.
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Which of the following is NOT a common outcome of gene transfer in bacteria?
Which of the following is NOT a common outcome of gene transfer in bacteria?
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What is the term for a bacterial cell that is unable to synthesize a specific nutrient, often due to a mutation in a gene involved in the biosynthesis of that nutrient?
What is the term for a bacterial cell that is unable to synthesize a specific nutrient, often due to a mutation in a gene involved in the biosynthesis of that nutrient?
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Study Notes
Microbial Genetics
- Genetics studies heredity, genes' roles in carrying, replicating, and expressing information.
- Genome includes chromosomes and plasmids.
- Chromosomes are DNA structures carrying hereditary information (genes).
- Genes are DNA segments (or RNA in some viruses) coding for functional products (primarily proteins, some RNA).
- DNA is a macromolecule of nucleotides (nucleobase, deoxyribose, phosphate).
- DNA forms a double helix with specific base pairing (A-T, C-G), making strands complementary.
- DNA's structure allows for accurate genetic information storage and cell division.
- Cellular metabolism translates genetic messages into proteins (DNA → RNA → Protein).
- Gene expression produces a gene's product (e.g., protein).
Genotype and Phenotype
- Genotype is an organism's genetic makeup (all DNA), encoding its characteristics.
- Genotype represents potential properties, not the properties themselves.
- Phenotype is the organism's actual expressed properties (e.g., chemical reactions).
- Phenotype is a manifestation of the genotype (e.g., E. coli's stx gene producing Shiga toxin).
- Microbes' phenotypes are mostly protein-based (enzymatic or structural).
DNA and Chromosomes
- Bacterial chromosomes are typically single circular DNA molecules.
- These chromosomes are looped, folded, and attached to the plasma membrane.
- E. coli's chromosome has ~4.6 million base pairs, exceeding cell size due to supercoiling.
- Genomes contain non-coding regions (STRs - Short Tandem Repeats).
- Genomics sequences and characterizes genomes.
The Flow of Genetic Information
- DNA replication creates identical offspring molecules from a parental double helix.
- DNA's base structure allows one strand to template the other during replication.
- Replication begins with DNA relaxation (topoisomerase/gyrase) and unwinding (helicase).
- DNA polymerase adds nucleotides, creating a new DNA strand.
- Replication occurs at replication forks, where the DNA molecule unwinds.
- Leading strands are synthesized continuously, while lagging strands are synthesized in Okazaki fragments.
Transcription in Prokaryotes and Eukaryotes
- Transcription is the RNA synthesis from a DNA template.
- Prokaryotes accomplish this in the cytoplasm.
- Eukaryotes perform this within the nucleus.
- Three RNA types are involved in protein synthesis (mRNA, rRNA, tRNA).
- mRNA carries the genetic code from DNA to ribosomes for protein synthesis.
- Eukaryotic mRNA undergoes splicing (removing introns and connecting exons).
Translation
- Translation decodes mRNA into amino acid sequences (protein synthesis).
- The genetic code relies on codons (three nucleotides coding for an amino acid).
- tRNA molecules carry anticodons matching mRNA codons and specific amino acids.
- Ribosomes facilitate amino acid assembly into polypeptide chains (peptide bonds).
Regulation of Gene Expression
- Cells regulate gene expression, only producing proteins as needed.
- Constitutive genes (60-80% of genes) are constantly active and produce products at set rates (essential enzymes).
- Regulation is necessary for other genes to produce enzymes only when needed (e.g., Trypanosoma).
- Pre-transcriptional control through induction or repression, affecting mRNA transcription (e.g., operon model).
- Operons are groups of genes transcribed together.
- Operons contain structural genes, a promoter (where RNA polymerase starts transcription), and an operator.
- Operons are regulated by inducible operons (e.g., lac operon) or repressible operons (e.g., tryptophan operon), controlling gene activation or repression.
- Positive regulation of the lac operon involves cAMP and CAP that are activated in the absence of glucose.
DNA Changes and Mutations
- Bacterial DNA changes through mutations (spontaneous alterations) or horizontal gene transfer (acquiring DNA from other organisms).
- Mutations lead to variation in biofilm formation, pathogenicity, and antibiotic resistance.
- Mutations can be either beneficial, neutral, or harmful.
- Mutagens (e.g., chemicals, radiation) increase the mutation rate.
Genetic Transfer
- Genetic transfer involves exchanging genes between DNA molecules, creating new combinations.
- Transformation involves bacteria taking up "naked" DNA from the environment (e.g., Griffith's experiment using Streptococcus pneumoniae).
- Conjugation is a direct cell-to-cell transfer of genetic material (plasmids, often in F+ cells) assisted by structures like sex pili (e.g., F factor in E. coli).
- Transduction relies on viruses (bacteriophages) to transfer bacterial DNA between cells via their life cycles (generalized or specialized).
Transposons
- Transposons are DNA segments that move locations within or between chromosomes.
- They can disrupt cellular functions by inserting themselves into genes.
- Transposons are a form of genetic exchange.
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Description
Explore the fundamentals of microbial genetics in this quiz. Understand the roles of genes and chromosomes in heredity, as well as the processes of DNA replication and protein synthesis. This quiz also covers the concepts of genotype and phenotype—crucial for understanding genetic variation.
