Answer:
Explanation:
A. Inactivation of an enzyme that degrades M-Cyclin.
M-phase cyclins form M-CDK complexes and drive the cell's entry into mitosis from G2 phase as non-degradation of M-Cyclin resulting from inactivated enzyme can only result in constitutive entry of the cell in to M phase instead cell cycle being arrested at G2 phase,
B. Inactivation of the Wee-1 kinase.
Wee1 is a nuclear kinase that plays a key role in regulating cell cycle progression. Wee1 inhibits the entry of the cell into M phase by inhibiting Cdk1. Wee1 phosphorylates Cdk1 there inhibiting the kinase activity of Cdk1 which is essential for progression from G2 to M phase. As such any mutation of wee1, and the resulting loss of activity will result in premature entry of cells into M phase instead of getting arrested at the G2 phase resulting in smaller yeast cell.
C. Inactivation of the Cdc25 phosphatase
CDC25 phosphatases removes inhibitory phosphate residues from cyclin dependent kinases resulting in the activation of CDKs which causes the cells in G2 phase to entry to M phase. Mutation in CDC25 phosphates removes the ability of CDC25 to remove phosphate residues from CDKs thus preventing the entry into M-phase.
Therefore, mutant phenotype of cell cycle arrest prior to M phase can only result form mutation in
Cdc25 phosphatase(option 3)
Do you have a like text book for this for me to answer?
The life expectancy has been rising. There is an improvement by two-thirds n life expectancy age since 1881. This is the same trend generally in the developing world. This is attributed to improvement in other indicators such as sanitation, health care and literacy rates that have improved the lifestyles of the people significantly.
Answer:
A closed system is a physical system that does not allow transfer of matter in or out of the system, though, in different contexts, such as physics, chemistry or engineering, the transfer of energy is or is not allowed.
