2) Is the following statement TRUE or FALSE? Explain your answer. “The cell-cycl

Question

2) Is the following statement TRUE or FALSE? Explain your answer. “The cell-cycle control system operates primarily by a timing mechanism, in which the entry into one phase starts a timer set for sufficient time to complete the required tasks. After a given amount of time has elapsed, a molecular “alarm” triggers movement to the next phase.”

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3) Describe the roles of p53 and p21 in control of the cell cycle.

Explanation / Answer

2)Ans:False.

The cell-cycle control system does use a timing mechanism of sorts, but it also uses various surveillance and feedback mechanisms (checkpoints).

3) Role of p53 in control of the cell cycle:

p53, also known as TP53 or tumor protein is a gene that codes for a protein which regulates the cell cycle and performs the function of tumor suppression.

It has a major role in suppression of cancer in multicellular organisms.It also plays an important role in cell cycle control and apoptosis

DNA damage and other stress signals may trigger the increase of p53 proteins, which have three major functions:

The growth arrest stops the progression of cell cycle, preventing replication of damaged DNA. During the growth arrest, p53 may activate the transcription of proteins involved in DNA repair. Apoptosis is the "last resort" to avoid proliferation of cells containing abnormal DNA.

p53 is also directly involved in DNA repair. One of its transcriptional target gene, p53R2, encodes ribonucleotide reductase, which is important for both DNA replication and repair.

Role of p21 in control of the cell cycle:

p21 is also known as cyclin-dependent kinase inhibitor 1 or CDK-interacting protein 1.

It is a cyclin-dependent kinase inhibitor that inhibits the complexes of CDK2 and CDK1 p21-activated kinases (PAKs) are also effectors for GTPases Cdc42 and Rac.

These effectors are responsible for cell morphology, motility, survival, gene transcription, apoptosis, and hormone signaling along with other processes.

The p21 protein binds to and inhibits the activity of cyclin-CDK2, -CDK1, and -CDK4/6 complexes, and thus functions as a regulator of cell cycle progression at G1 and S phase.

In addition to growth arrest, p21 can mediate cellular senescence

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