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Which of the following statements is false?

A. DNA replication occurs only in S phase.
B. The activation of S-Cdk helps prevent the onset of M phase.
C. The activation of S-Cdk helps prevent DNA replication occurring more than once each cycle.
D. The activation of S-Cdk initiates DNA replication.

Respuesta :

B) option is false

Explanation:

All events of cell cycle is regulated by a heterodimeric protein complex called cyclin CDKs, cyclin is the regulatory subunit which binds to CDKs and activate them whereas CDKs(cyclin dependent kinases) is the catalytic subunit where cyclin bound CDKs become active and act as serine threonine kinase and phosphorylate target proteins

The activation of S-Cdk helps prevent the onset of M phase because S phase cyclin CDK complex trigger initiation of DNA replication from pre replication complex and inhibits rebinding of components of pre replication complex

marianaegarciaperedo

Cyclins are regulator molecules that control the cell cycle in its different stages. Cyclins get associated with enzymes to produce a cascade of events. The incorrect option is B. The activation of S-Cdk helps prevent the onset of M phase.

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  • Many molecules regulate the cell cycle during the different stages of the mitosis process to make it possible.

  • There are too many factors interacting, activating, and deactivating to pass from one stage to another.

  • Cyclins are cell cycle regulator proteins that control the cell during the process of division. Different types of cycling act on different stages.

  • When the cell is going through one of the stages, the only cyclin in high levels is the one that is regulating that part of the cycle.

  • Once that stage is over, that cyclin concentration decreases, and the following one increases.

  • But if any step was not correctly performed, the cell can not pass to the following one.

  • Cyclins associate with enzymes, activating them, to generate a cascade of events involved in that stage.

  • Kinases, Cdk, are enzymes that depend on cyclins and that remain inactive until cyclins are present.

  • The enzyme becomes functional when the cyclin binds it. Then, the kinase can accomplish its functions.

  • During the S stage of the interphase occurs the DNI replication process.

  • At this point, also occurs the synthesis of histones and other associated proteins.

  • This is the only stage where the DNI molecule is replicated.

  • S phase cyclins are in charge of regulating the stage of DNA replication.

  • The association between S cyclins to Cdk enzymes is the S-Ckd complex.

  • If the cell does not go through the S phase, the cyclins of this stage are not activated. And if S phase cyclins are not active, the cell can not go to the G2 phase.

  • The cell remains in the S phase until the DNA replication process is correctly done. And if it does not occur, the cell suffers programmed cell death

Options:

A. DNA replication occurs only in S phase. TRUE

B. The activation of S-Cdk helps prevent the onset of M phase. FALSE

C. The activation of S-Cdk helps prevent DNA replication occurring more than once each cycle. TRUE

D. The activation of S-Cdk initiates DNA replication. TRUE

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