Question

The number of cyclins of each type (G1/S cyclins, S cyclins, M cyclins) vary during different stages of the cell cycle?

True or False?

What is the function of SCF?

A. removes a H+ from a molecule

B. adds a phosphate to a molecule

C. add ubiquitin to a molecule

D. removes a phosphate from a molecule

Select all of the following which can inactivate a cyclin dependent kinase (cdk)

A. remove an inhibitory protein

B. remove the cyclin from the cdk

C. remove an inhibitory phosphate

D. add an inhibitory phosphate

E. add an inhibitory protein

What stage of mitosis does APC/cdc20 stimulate? Use one word: for example: prophase

Answer 1

1). The number of cyclins of each type (G1/S cyclins, S cyclins, M cyclins) vary during different stages of the cell cycle? ---> TRUE

Specific steps in cell cycle are controlled by cyclines, which act through cyclin-dependent kinases (CDKs). Cyclins are the regulatory proteins to which the cyclin-dependent kinases (CDKs) bind and activate the CDKs. The kinase activity of CDK is less in the absence of cyclins. The concentration of cyclins changes throughout the cell cycle as each regulates specific steps in the cell cycle. For example, the concentration of cyclin G1/S raises at the end of the G1 phase and decreases by the mid of the synthesis phase.

Cyclin D act through extracellular signals, but the other cyclins operate according to the predetermined schedule. Once the decision has been made to pass through the G1 phase, all the other cyclins accumulate rapidly followed by their immediate destruction, thus allowing the cycle to move only in one direction.