Because they cannot rotate, each peptide bond holds 6 atoms in a plane.

However, most possible angles of Phi (φ) and Psi (ψ) are impossible due to clashes

between atoms. These balls are much smaller than the atoms they represent.

TLS Online TPP Program

#Id: 8848

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 8849

#Unit 2. Cellular Organization

Phosphorylation of MCM helicase activators by G1/S phase CDKs and S phase CDKs, prevents reloading of MCM helicases (ensuring that replication from each origin occurs only once during each cell cycle)

TLS Online TPP Program

#Id: 8850

#Unit 2. Cellular Organization

Geminin 

a small protein,, that contributes to the inhibition of re-initiation at origins until cells complete a full cell cycle.

TLS Online TPP Program

#Id: 8851

#Unit 2. Cellular Organization

Geminin is expressed in late G1; it binds to and inhibits Cdt1 preventing reloading of the MCM helicase.

TLS Online TPP Program

#Id: 8852

#Unit 2. Cellular Organization

Geminin contains a destruction box at its N-terminus that is recognized by APC/Ccdh1, causing it to be ubiquitinylated in late anaphase and degraded by proteasomes.

TLS Online TPP Program

#Id: 8853

#Unit 2. Cellular Organization

Cohesins 

The protein ring complexes that establish linkages between sister chromatids