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Questions and Answers
What are the two main forms of plasmids based on their structure?
Circular and Linear
What is the primary function of R-plasmids?
To carry one or more antibiotic resistance genes
What is the characteristic of conjugative plasmids?
Ability to transfer to other bacteria
What is the range of sizes of naturally occurring plasmids?
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What is the role of chromosomally encoded enzymes in plasmid replication?
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What is the purpose of the genes encoded by a plasmid?
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Why are plasmids considered nonessential?
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What is the term for the number of different plasmids present in a cell?
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What is the characteristic of transposable elements?
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Where can transposable elements be found?
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Study Notes
Microbial Genetics
- MBG 3711 Lecturer: Ms. Sylvia Nafuka
- Contact hours: Timetable slot D, 4 lecture periods
- Important dates: Online quizzes and face-to-face tests
Introduction to Microbial Genetics
- The structure and organization of microbial genomes
- Microbial phenotypes are designated by a non-italicized 3-letter abbreviation
- Variation in phenotype may be designated by superscripts (e.g. "+", "-", "R", "S")
Structure of Nucleic Acids
- Nucleic acid molecules contain instructions for an organism's development, life, and reproduction
- Eukaryotic organisms store DNA in the nucleus and organelles like mitochondria
- Bacterial DNA forms a tangle known as a nucleoid
- Plasmids are small loops of DNA that can be transmitted from one cell to another
Bacteria Gene Content and Scales of Genome Organisation
- Average gene content: 3,100 genes per genome
- Lowest number of genes: Mycobacterium genitalium (480 genes)
- Highest gene content: Brady rhizobium japonicum (8,317 genes)
- Base pair composition average: 22.4% GC
- Variation in base composition between leading and lagging strands
DNA Supercoiling
- Double-stranded DNA twisted into supercoils by topoisomerases
- Positive supercoiling: DNA molecule twisted about its axis in the opposite direction
- Negative supercoiling: DNA molecule twisted about its axis in the same direction
- Type 1 and Type 2 topoisomerases: involved in DNA replication and decatenation
Plasmid Classifications
- Based on structure: Circular and Linear
- Based on function: R-plasmids, Col-plasmids, and Cryptic plasmids
- Based on ability to transfer: Conjugative and Non-conjugative
- Based on coexistence: Compatible and Incompatible
Plasmid Characteristics
- Naturally occurring plasmids range from 1 kbp to over 1 Mbp
- Almost all plasmids are circular, supercoiled, and double-stranded DNA molecules
- Own origin of replication, but rely on chromosomally encoded enzymes
- Genes encoded by a plasmid function to direct initiation of replication and partitioning of replicated plasmids between daughter cells
- Plasmids do not have an extracellular form and exist inside cells as free DNA
- Copy number is controlled by genes on the plasmid and interactions between the host and the plasmid
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Description
This quiz assesses knowledge on microbial genetics, covering topics such as genetic principles, microbial genetics, and genetic mechanisms. It is designed for students taking MBG 3711 Microbial Genetics.
