Answer:
a mutation that blocks the GTPase activity of Ras
Explanation:
A G protein in inactive state is GDP bound but as soon as a guanine exchange factor (GEF) exchanges it with GTP it gets activated which means that in GTP bound state it is active. G - protein has endogenous GTPase activity. Upon interaction of GAP, the GTPase activity of this protein is exhibited. When GAP is present, hydrolysis of GTP into GDP occurs which leads to inactivation of G protein. A mutation which will block GTPase activity of Ras will therefore result in constitutive active signaling even in the absence of ligand binding to it's receptor. In such scenario, GTP will not be hydrolyzed into GDP so signaling will be up-regulated.
Answer:
E. that area of the membrane is in the absolutely refractory period.
Explanation:
Refractory period is a period during which neuron cell cannot be stimulated (depolarized). This is why the action potential can only travel in one direction from the neuron body towards axon.
Refractory period occurs because of the inactivation of voltage-gated sodium channels (while action potential is at its peak) which cannot be open for a certain period of time. and membrane cannot be depolarized.
Answer:
The correct answer will be option-A.
Explanation:
Lac operon is a set of genes arranged sequentially for lactose metabolism in E.coli. The lac operon gets activated in the presence of lactose as the lac operon consists of three enzyme coding genes called lacZ which codes for the β-galactosidase enzyme, lacY which codes for lactose permease, lacA which codes for acetyltransferase along with a regulatory gene called lacI which codes for repressor proteins.
The repressor proteins bind to the operator and control the transcription. When it binds to operator its huts off the transcription. If a mutation occurs in the laci gene then the protein will lose the machinery which will turn off the activity of enzymes and will lead to the constitutive expression of the genes irrespective of the inducer present or not.
Thus, option-A is the correct answer.
Non vascular plants are very small because their lack of a vascular system means they do not have the mechanics required for transporting food and water far distances. ... Non vascular plants are small, simple plants without a vascular system. They do not have a phloem or xylem.
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.
