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13BIS101S2013GeneRegulLect13-1

Material bacterial chromosomes the bacterial

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Unformatted text preview: information in bacteria can be used to identify and map genes. can Plasmids: Bacteria contain extrachromosomal elements called plasmids or F factors. Plasmids play a important role in the transfer of genetic material from male (F+ or Hfr) bacteria to female bacteria. material Bacterial chromosomes: The bacterial chromosome is circular, not linear. linear. Conjugation: Chromosomal material can be passed through a “sex pilus” from donor (or male) bacterium to recipient (female) cell. By opening the circular chromosome at any point on its circumference it can be transferred into the female cell as a "linearly permutation” of the circle. transferred Complementation: Complementation can occur when the wild type gene Complementation is placed in the presence of a mutant gene, without recombination occurring (e.g. on a plasmid). In this instance, the wild type phenotype is restored and it is said that the wild type gene “complements” the mutant phenotype. Complementation analysis can be used to determine how many genes are involved in a particular phenotype. many BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 13 Merodiploid (partial diploid) F-factors are like minichromosomes (plasmids) in E. chromosomes coli. coli. Using the plasmid, F-lac, to pick Using Fup some of the different lac mutations, Jacob and Monod were able to construct merodiploids (partial diploids) to merodiploids study the nature of each mutation. These studies revealed that constitutive mutants mapped to two different locations in the operon. Some were located in the lacI gene while others were lacI located in the intergenic region designated "O". designated ". Bacterial F-factors-Conjugation BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 14 Lac Regulation Movie Allolactose-Repressor Binding-Allosteric Confirmational Change BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 15 Merodiploid Complementation 1 In this merodiploid, the I- gene makes no functional repressor. However, In because the repressor protein is a diffusible gene product, iit can act at t diffusible both operators (O+) to control expression of the Z+ gene on both both to chromosomes. The repressor protein is said to act in “trans” or I+ is or “trans-dominant” to I-. to I- P+ O+ Z+ I P O Z + + + + = iinducible control of β-gal nducible BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 16 Lac Repressor Mutation Movie BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 17 Lactose Repressor Lactose Lac...
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