Cell Cycle Flashcards
What are the cellular consequences of prenatal Zika virus infection?
oddly shaped nucleus, leading to the inability of the chromosomes to separate properly, resulting in triploid cells that are not viable, leading to cell death
What are the phenotypic consequences of prenatal Zika virus?
decreased brain tissue and specific pattern of brain damage, causing severe microcephaly, seizures, auditory defects, scarring at the back of the eye, limited mobility, and the infection of neural system cells
How do growth factors promote the G1 to S transition in normal cells?
by activating the receptor tyrosine kinase (RTK) pathway; when a growth factor is present, it brings each half of the dimers together, causing the receptors to transphosphorylate each other, then phosphorylate a variety of downstream targets until, ultimately, a series of additional kinases ultimately phosphorylate transcription factors (or the cofactors for a transcription factor), causing the transcription factor to promote the transcription of downstream genes
How do p53 and CDK inhibitors like p21 prevent cells from entering S phase when they have extensive DNA damage?
p53 induces the expression of p21 inhibitors. p21 prevents the activity of the CDK4-Cyclin D complex, preventing it from phosphorylating Rb protein. The Rb protein remains associated with E2F, preventing entry into the S phase.
What are “tumor suppressors” and what kinds of roles do they play during normal development or homeostasis?
Tumor suppressors like p53 regulate the cell cycle. During normal development, they serve as checkpoints for quality control and help prevent cancer.
How does tumor suppressor copy number relate to cancer susceptibility in humans and other organisms?
Some organisms have significantly more cells than humans, but also have larger amounts of copies of TP53, which regulates the cell cycle more closely than humans. Body size and life span are not correlated with cancer risk due to Peto’s Paradox.
What stage are cells normally in?
G1
At what point do cells constantly cycle?
early development
What are the three functions of p53?
inducing expression of p21, the CDK inhibitor
inducing the expression of DNA repair genes
inducing the expression of apoptosis genes
What happens to lamins after phosphorylation?
They become soluble in cytosol, opening the cell so chromosomes can be segregated during division.
What phosphorylates the retinoblastoma protein?
CDK4-Cyclin D and CDK2-Cyclin E
What does phosphorylated Rb protein do?
Releases the E2F transcription factor, which regulates the S phase
