#Question id: 1513
#Unit 4. Cell Communication and Cell Signaling
The kinase activity of ATM is activated in response to DNA damage due to various stresses (e.g., UV irradiation, heat). Activated ATM then triggers following pathways leading to arrest in G1.
A. Chk2 is phosphorylated and, in turn, phosphorylates Cdc25A, thereby marking it for degradation and blocking its role in CDK2 activation.
B. Phosphorylation of p53 stabilizes it, permitting p53-activated expression of genes encoding proteins that cause arrest in G1, promote apoptosis, or participate in DNA repair.
C. Controlling the pool of p53, ATM phosphorylates MDM2 to inactivate it, causing increased stabilization of p53. Another protein p14ARF inhibits the activity of Mdm2 thus stabilizing p53.
Based on the above information, which one of the following statements is correct?
#Question id: 19046
#Unit 13. Methods in Biology
#Question id: 13173
#Unit 10. Ecological Principles
#Question id: 33379
#Unit 1. Molecules and their Interaction Relevant to Biology
#Question id: 4966
#Unit 11. Evolution and Behavior
If it were possible to conduct sophisticated microscopic and chemical analyses of microfossils found in 3.2-billion-year-old stromatolites, then within such microfossils, one should be surprised to observe evidence of:
I. double-stranded DNA
II. a nuclear envelope
III. a nucleoid
IV. a nucleolus
V. nucleic acids