Fossils are the impression of dead living organisms on the surface. Fossils provide the direct evidence of evolution.
The fossil records reveals the features of ancestor and can be used to compare against the living descendants.The gradual change in the species as compared to its ancestor can be determined by the fossil record Hence, fossils record can provide the common ancestor to many species.
Cell cycle is mainly divided into two phases-Interphase and Mitotic phase
Interphase is the preparatory phase whereas mitotic phase is the dividing phase
Various cyclins and Cdks are regulated during these phases
M-Cdks stands for Mitotic Cyclin Dependent Kinases which helps in cell cycle regulation
Cdks are the catalytic subunit bound to the regulatory subunit(cyclins)
Mitosis includes four stage namely Prophase,Metaphase,Anaphase and Telophase
During the Anaphase stage separation of sister chromatids occurs due to the destruction of a protein called cohesin
Destruction of cohesin is catalysed by an enzyme called separase
Prior to anaphase securin binds to separase and inhibits its activity
The APC(anaphase promoting complex) with specificity factor Cdc20 tragets securin for polyubiquitination which then degraded by proteasome
The separase released becomes active and breaks the bridge between sister chromatids
Movement of sister chromatids occurs towards their respective poles
In late anaphase,specific phopshates called Cdc14 removes the regulatory phosphate group from cdh1 specificity factor and therefore Cdh1 becomes active
Active Cdh1 specificity factor binds to and activate APC(anaphase promoting complex)
Cdh1 bound APC catalyse ubiquitination of mitotic cyclins
As the mitotic cyclins are degraded by the proteasome,onset of telophase starts
Wee1 is a kinase enzyme which comes into consideration in case of fission yeast
Wee 1 phosphorylates the inhibitory site of M-Cdk which further leads the cells to enter into mitosis
