Directional Natural selection

Directional selection favors individuals at one extreme of a phenotypic distribution that have greater reproductive success in a particular environment.

TLS Online TPP Program

#Id: 8636

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 8637

#Section 3: Genetics, Cellular and Molecular Biology

The G1 cyclin-CDK complex (Cln3-CDK in yeast) stimulates the formation of G1/S phase cyclin-CDKs, which initiate bud formation, centrosome duplication, and DNA replication.

TLS Online TPP Program

#Id: 8638

#Section 3: Genetics, Cellular and Molecular Biology

Once sufficient Cln3 is synthesized from its mRNA, Cln3-CDK complexes phosphorylate and inactivate the transcriptional repressor Whi5.

TLS Online TPP Program

#Id: 8639

#Section 3: Genetics, Cellular and Molecular Biology

Phosphorylation of Whi5 promotes its export out of the nucleus, allowing the transcription factor complex SBF to induce transcription of the G1/S phase cyclin genes CLN1 and CLN2.

TLS Online TPP Program

#Id: 8640

#Section 3: Genetics, Cellular and Molecular Biology

In vertebrates, Rb is the major guardian of the cell cycle, integrating information about DNA damage and cell growth

TLS Online TPP Program

#Id: 8641

#Section 3: Genetics, Cellular and Molecular Biology

Rb binds the activation domains of a E2F transcription factors, in the cytoplasm to prevent them from turning on the genes required for cell cycle progression.