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Questions and Answers
What does one codon in a gene specify?
What does one codon in a gene specify?
What is the total number of different codons possible with a four-letter alphabet?
What is the total number of different codons possible with a four-letter alphabet?
Which of the following statements about bacterial colonies is true?
Which of the following statements about bacterial colonies is true?
How can mutations be easily produced in bacteria?
How can mutations be easily produced in bacteria?
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What is the significance of environmental conditions on genetic expression?
What is the significance of environmental conditions on genetic expression?
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Why is the short generation time of bacteria advantageous for genetic research?
Why is the short generation time of bacteria advantageous for genetic research?
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What role does nutrient availability play in the genetic expression of organisms?
What role does nutrient availability play in the genetic expression of organisms?
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What is the primary role of the accessory genome in bacteria?
What is the primary role of the accessory genome in bacteria?
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Which mechanism allows bacteria to acquire genetic material from other strains?
Which mechanism allows bacteria to acquire genetic material from other strains?
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Which statement about bacteriophage DNA is true?
Which statement about bacteriophage DNA is true?
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What distinguishes DNA replication in bacterial cells from eukaryotic cells?
What distinguishes DNA replication in bacterial cells from eukaryotic cells?
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Which of the following is NOT considered a virulence factor in bacteria?
Which of the following is NOT considered a virulence factor in bacteria?
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How do plasmids contribute to antibiotic resistance in bacteria?
How do plasmids contribute to antibiotic resistance in bacteria?
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What is a characteristic of the bacterial chromosome?
What is a characteristic of the bacterial chromosome?
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Which of the following statements about genotype and phenotype is true?
Which of the following statements about genotype and phenotype is true?
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What feature of bacterial cells typically aids in their rapid adaptation to environmental changes?
What feature of bacterial cells typically aids in their rapid adaptation to environmental changes?
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What is the primary role of plasmids in bacteria?
What is the primary role of plasmids in bacteria?
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How do plasmids differ from bacterial chromosomes?
How do plasmids differ from bacterial chromosomes?
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Which statement about bacteriophages is true?
Which statement about bacteriophages is true?
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What role do plasmids play in antibiotic resistance?
What role do plasmids play in antibiotic resistance?
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Which of the following is an example of a virulence factor encoded by plasmids?
Which of the following is an example of a virulence factor encoded by plasmids?
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What is the structure of plamids?
What is the structure of plamids?
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What does the base pairing rule dictate in DNA?
What does the base pairing rule dictate in DNA?
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What characteristic of bacteriophages allows them to transfer genes between bacteria?
What characteristic of bacteriophages allows them to transfer genes between bacteria?
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Study Notes
Bacterial Genetics Overview
- Molecular structure of DNA consists of base pairing and has a 5’→3’ orientation.
- Bacterial cell contains DNA organized as the bacterial genome, encompassing chromosomes, plasmids, and bacteriophage DNA.
Bacterial Genome Composition
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Bacterial Chromosome:
- Small, circular, double-stranded DNA found in the cytoplasm.
- Self-replicating and typically less than 5Mb in size.
- Most bacteria are haploid, possessing one chromosome (exceptions exist like Vibrio cholerae with two).
- The chromosome is supercoiled and packaged in the nucleoid, totaling a length of 1mm.
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Core vs. Accessory Genome:
- Core genome consists of essential genes on the chromosome necessary for survival.
- Accessory genome includes genes on plasmids/bacteriophages that provide selective advantages (e.g., antibiotic resistance, virulence factors).
Genetic Code
- Codons consist of three nucleotides that encode amino acids (e.g., ATG = methionine).
- There are 64 different codons formed from the nucleotide combination.
- The genetic code specifies how mRNA nucleotides relate to amino acids in polypeptides.
Genotype and Phenotype
- Genotype: Refers to the organism's inherited genetic information and actual DNA sequence.
- Phenotype: Represents observable properties influenced by genotype and environmental conditions (e.g., Bacillus anthracis expresses a capsule in vivo).
Advantages of Bacteria in Genetic Studies
- Bacteria are haploid, simplifying the production of mutant phenotypes.
- Short generation time allows for rapid experimentation.
- Asexual reproduction ensures progeny are genetically identical.
- Can be grown on agar plates, enabling easy colony isolation and selection of rare mutants.
- Dormancy allows prolonged storage.
- DNA exchange capability facilitates horizontal gene transfer.
Bacterial Colonies
- Each colony represents clones of the original bacterium, resulting in millions of genetically identical bacteria.
Plasmids
- Plasmids are extrachromosomal, closed, circular, double-stranded DNA located in the cytoplasm and vary in size (5 to 500 kb).
- They replicate independently of bacterial chromosomes and can transfer between bacterial species.
- Encode non-essential traits impacting pathogenic properties, such as antibiotic resistance and toxin production (e.g., tetanus toxin, anthrax capsule).
Bacteriophages
- Bacteriophages are viruses that infect bacteria and contain extrachromosomal genetic material.
- Phage genome sizes range from 2 to 200 kilobases and may consist of double or single-stranded DNA.
- Some encode exotoxins, such as cholera toxin in Vibrio cholerae.
DNA Structure
- DNA has a double helical structure with grooves between strands.
- Base pairing rules: A pairs with T, and G pairs with C.
- Each base pair (A-T and G-C) is called a complementary base pair.
- 5' end features a phosphate group, while the 3' end lacks a phosphate at its last nucleotide.
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Description
This quiz covers key concepts in bacterial genetics, focusing on the molecular structure of DNA, the DNA replication process, and the connection between genotype and phenotype. Additionally, it explores the various pathways of inter-bacterial gene transfer. Test your understanding of these fundamental topics in microbial genetics.
