Lecture #11 - Prokaryotic Gene Expression Ii

Ogan Gurel, MD Biology 301 Lecture # 11 Roosevelt University

Biology 301 Cellular and Molecular Biology Fall 2002

Lecture # 11: Prokaryotic Gene Expression II Bacteria

Ogan Gurel, MD Biology 301 Lecture # 11 Roosevelt University

Overall outline  Introduction to Bacteria  Genetic Recombination in Bacteria  Regulation of Transcription

Ogan Gurel, MD Biology 301 Lecture # 11 Roosevelt University

Introduction to Bacteria Bacterial structure Bacterial life cycle E. coli DNA E. Coli dividing: binary fission Plasmids Replication of the bacterial chromosome

Bacterial structure • Prokaryotes are distinguished by having no membrane-bound organelles. • The DNA genome is gathered in a central region called the nucleoid. • Bacteria are also uniquely characterized by a rigid cell wall which serves to resist osmotic stress. • Bacteria can be classified in terms of their cell-wall components and in terms of their shape.

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Bacterial life cycle • Bacterial growth (generally exponential) usually involves asexual reproduction (binary fission); sexual reproduction via gene transfer is rarer. • The resulting semi-log growth curve involves lag, logarithmic and stationary phases.

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

E. coli DNA

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

E. Coli dividing: binary fission

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Plasmids

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Replication of the bacterial chromosome

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Genetic Recombination in Bacteria

Ogan Gurel, MD Biology 301 Lecture # 11 Roosevelt University

Detecting genetic recombination in bacteria Transduction Conjugation: Bacterial mating Recombination in E. coli Insertion sequences, the simplest transposons Insertion of a transposon and creation of direct repeats Anatomy of a composite transposon

Detecting genetic recombination in bacteria

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Transduction (during lysis)

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

(during lysogeny)

Conjugation: Bacterial mating

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Recombination in E. coli

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Recombination in E. coli

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Insertion sequences, the simplest transposons

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Insertion of a transposon and creation of direct repeats

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Anatomy of a composite transposon

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Ogan Gurel, MD Biology 301 Lecture # 11 Roosevelt University

Regulation of Transcription Regulation of a metabolic pathway The lac operon: regulated synthesis of inducible enzymes cAMP Positive control: cAMP receptor protein The trp operon: regulated synthesis of repressible enzymes

Regulation of a metabolic pathway

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

The lac operon: regulated synthesis of inducible enzymes • Regulation of gene expression often occurs at the level of transcription. • The most common strategy is to control the binding of RNA polymerase to the promoter or to block its precessive activity along the operon. • Eukaryotic regulatory mechanisms are more complicated and involve a variety of DNA enhancer elements and protein transcription factors. • The lac operon depicted here is a prototypical system.

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

cAMP

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

Positive control: cAMP receptor protein

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University

The trp operon: regulated synthesis of repressible enzymes

Ogan Gurel, MD Biology 301 Lecture # 10 Roosevelt University