Answer:
Negative inducible.
Explanation:
Operon may be defined as the cluster pf genes that are expressed by the single RNA polymerase. The operon includes in the example of the the polycistronic genes.
Negative inducible operon includes the binding of regulatory protein with the DNA and inhibits transcription. The regulatory protein binds with the operator that prevents RNA polymerase transcription. The mutation in the negative inducible operon prevents the binding of repressor to the small molecule.
Thus, the correct answer is option (a).
Answer:
Different plants have different strategies for the dispersal of seeds. It dependents upon the environment in which they are growing. The three different ways of seed dispersal are:
1. Gravity: As, the fruits in the seeds gets ripen, they fall from the trees or plants because of the action of gravity acting on them. This mechanism is called as abscission. The seeds gets ejected or comes out of the fruit after degradation and decomposition of the fruit.
2. Wind and water: Wind and water are two agents which facilitates the transfer of seeds from one location to the other location.
3. Animals and birds: The animals and birds consume fruits along with seeds. They leave the seeds to different location, in the form of whole seed, partially consumed fruit or in the form of seed present in their biological waste.
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)
levels become unnecessary, a condition known as Acidosis happens.