James Hutton and Charles Lyell – Uniformitarianism

Darwin was greatly influenced by Lyell’s teachings, and he adopted uniformitarianism in his thinking about evolution.

TLS Online TPP Program

#Id: 6278

#Unit 3. Fundamental Processes

The complete enzyme or holoenzyme in E. coli has a molecular weight of ,460 kD. The holoenzyme (a2bbws) can be separated into two components: the core enzyme (a2bbw) and the sigma factor (the s polypeptide), which is concerned specifically with promoter recognition.

TLS Online TPP Program

#Id: 6279

#Unit 3. Fundamental Processes

With s subunit, the holoenzyme worked equally well on both types of DNA

TLS Online TPP Program

#Id: 6280

#Unit 3. Fundamental Processes

Core enzyme binds indiscriminately to any DNA. Sigma factor reduces the affinity for sequence-independent binding and confers specificity for promoters.

TLS Online TPP Program

#Id: 6281

#Unit 3. Fundamental Processes

Holoenzyme binds to promoters much more tightly, with an association constant ,1000 times higher on average and a half-life that can be as long as several hours

TLS Online TPP Program

#Id: 6282

#Unit 3. Fundamental Processes

significantly higher dissociation rate at 25C than at 37C, and a much higher dissociation rate at 15C. Because high temperature promotes DNA melting

TLS Online TPP Program

#Id: 6283

#Unit 3. Fundamental Processes