Laboratory strains of the model organism Escherichia coli that are resistant to
ID: 188038 • Letter: L
Question
Laboratory strains of the model organism Escherichia coli that are resistant to antibiotics are very often used in research laboratories as well as in the biotechnology industry. If cultures of such bacteria were allowed to contaminate the environment uncontrollably, it is possible that at some point, pathogenic bacteria such as Neisseria meningitidis (which causes meningitis and can cause death, especially in children) could acquire the same antibiotic-resistance gene, causing a meningitis outbreak that is difficult to treat. In this scenario, which of the following mechanisms is a more likely source of the antibiotic- resistance gene in N. meningitidis? a. Random new gene generation b. Intragenic mutation c. Gene duplication d. DNA segment shuffling e. Horizontal gene transfer Mitochondria and chloroplasts are thought to have evolved from free-living aerobic bacteria that were engulfed by an ancestral anaerobic cell and established a mutually beneficial (symbiotic) relationship with it. Which of the following statements is NOT true about these organelles? a. They are similar in size to small bacteria. b. They have their own circular genomic DNA. c. They have their own ribosomes. d. They have their own transfer RNAS. e. They are found in all eukaryotes.Explanation / Answer
1. E. Horizontal gene transfer.
In horizontal transfer, genes can be passed between individual members of different species by processes such as conjugation, transformation, and transduction. Some pathogenic bacteria have acquired, the genes necessary for infection through horizontal gene transfer, whereas others have acquired genes that confer resistance to antibiotics.
2. E. They are found in all eukaryotic cells.
Although mitochondria occurs throughout the eukaryotes but chloroplasts are not found in all eukaryotes. They are absent in animal cells, fungi and most of the protozoans.
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