Answer:
Some brain cells start dying less than 5 minutes after their oxygen supply disappears. As a result, brain hypoxia can rapidly cause severe brain damage or death.
Explanation:
Answer:
It activates Cdc25, which in turn activates more M-Cdk
Explanation:
Cyclin are enzymes that regulate cell cycle progression by the activation of cyclin-dependent kinases (CDKs). These cyclins have no enzymatic activity on their own but they can activate Cdks by binding and phosphorylating them. CDKs can be activated by phosphorylation of activating sites and/or dephosphorylation of inactivation sites. Moreover, M-phase cyclins are cyclins that form M-CDK complexes in order to modulate the cell's entry into mitosis. Cdc25 is a phosphatase involved in the eukaryotic cell cycle which is well-known to regulate the entry into and progression during S (DNA Synthesis) phase and mitosis. In this regard, it has been shown that mitotic phosphorylation of Cdc25 by M-Cdks increases its intrinsic phosphatase activity, thereby Cdc25 is able to remove inhibitory phosphates from M-Cdk and, consequently, activate more M-Cdks.
Answer:
"Brachiopoda"
Drosal and ventral valves; Individuals resemble clams; May have no anus
"Bryozoa"
Possesses a chitinous zoecium; Anus opening near mouth; Colonies resemble moss
<u>Answer</u>: B) the mass extinction of the dinosaurs 66 millions years ago
Macroevolution is a term used to define changes of whole taxonomic groups over long periods of time. The extinction of the dinosaur is not an example of this evolutionary process. The changes occurred over a relatively short period of time and did not involve changes in a taxonomic group, but rather their extinction.