Answer:
Constitutive activation is the alteration of a protein or signaling pathway such that it is functional or engaged even in the absence of an upstream activating event. For example, RasD is constitutively active because it cannot bind GAP and therefore remains in the GTP-bound, active state even when cells are not stimulated by growth factor to activate a receptor tyrosine kinase.
Constitutively active Ras is cancer promoting because cells will proliferate in the absence of growth factors, and thus normal regulatory mechanisms for cell proliferation are bypassed.
(a) A mutation that resulted in Smad3 binding Smad4, entering the nucleus, and activating transcription independent of phosphorylation by the TGFβ receptor would render Smad3 constitutively active.
(b) A mutation that made MAPK active as a kinase and able to enter the nucleus without being phosphorylated by MEK would render MAPK constitutively active.
(c) A mutation that prevented NF-KB from binding to IK-B or that allowed NF-KB to enter the nucleus and regulate transcription even when bound to IK-B would render NF-KB constitutively active.
Answer:
Temperatures gradient
Explanation:
There are distinct temperature gradient differences in the layers of atmosphere usually due to the main air molecule composition of the layers, the density of the molecules. The Troposphere the lowest layers is the densest and temperature decreases with increase in altitude. The stratosphere, on the other hand, has an increase in temperature with increase in altitude. Temperatures decrease with altitude in the mesosphere while the parameter increases with altitude in the thermosphere.
I don’t know why they make everyone type more than 20 characters but B sounds like the most reasonable answer.
Answer:
A pollen tube grows from the pollen grain into the ovary
Explanation:
Water is needed for fertilization in several plant groups because the sperm needs to swim to meet the non-motile eggs of the female organs.
<em>However in angiosperms, the pollen germinates and a structure known as pollen tube which contains the male gametophyte (sperm) grows into the ovary where the ovule is located and the male gametophyte is deposited in the ovule to initiate the fertilization process.</em>
<em>Hence, water is really not necessary for fertilization in the angiosperms.</em>
