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#Question id: 1249

As in all G protein–coupled signalling pathways, timely termination of the rhodopsin signalling pathway requires that all the activated intermediates be inactivated rapidly, restoring the system to its basal state, ready for signalling again. Which of the following mechanism does not terminate rhodopsin signalling?

#Unit 4. Cell Communication and Cell Signaling

  1. The complex composed of the inhibitory γ subunit of PDE and Gαt∙ GTP recruits two additional proteins, RGS9 and Gβ5, that together act as a GAP to enhance the rate of hydrolysis of bound GTP to GDP. Hydrolysis of GTP, in turn, causes release of the PDE γ subunit, which re-joins the PDE α and β subunits, terminating PDE activation.

  2. Light-triggered closing of the cGMP-gated cation channels causes a drop in the cytosolic Ca2+ concentration inside the rod cell. The drop in the intracellular Ca2+ concentration is sensed by a class of Ca2+-binding proteins known as guanylate cyclase–activating proteins, which bind to guanylate cyclase and stimulate its activity, thereby elevating the level of cGMP and causing the cGMP-gated ion channels to reopen.

  3. A major process that suppresses and helps to terminate the visual response involves phosphorylation of rhodopsin when it is in its activated (R*). Rhodopsin kinase, is the enzyme that catalyzes this phosphorylation reaction. Arrestin bound to the phosphorylated R* completely prevents interaction with Gαt, blocking formation of the active Gαt∙ GTP complex and stopping further activation of PDE.

  4. Binding of acetylcholine triggers activation of the Gαi subunit and its dissociation from the Gβγ subunit in the usual way. In this case, however, the released Gβγ subunit (rather than Gαi∙ GTP) binds to and opens the associated effector protein, a K+ channel. The increase in K+ permeability hyperpolarizes the membrane, which reduces the frequency of PDE activation.

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TLS Online TPP Program

#Question id: 4729

#Unit 8. Inheritance Biology

In the following example, 3 independently assorting genes A, B and C are known to govern coat color in mice. Homozygous recessive cc (albino phenotype) is epistatic over both gene A and B, What will be the expected frequency of non albino, in the progeny from cross of AaBbCc with genotype of AABbCc?
TLS Online TPP Program

#Question id: 4730

#Unit 8. Inheritance Biology

Cross is made between a pure breeding plant having red coloured male flowers with a pure breeding plant having white colored female flowers. All of these offspring are white colored flower. Upon selfing of these F1 red flower plant produced both red and white flower. Which of the following is conclusion of these cross?
TLS Online TPP Program

#Question id: 4731

#Unit 8. Inheritance Biology

A pure-breeding strain of squash that produced disk-shaped fruits was crossed with a pure breeding strain having long fruits. The F1 had disk fruits, but the F2 showed a new phenotype, sphere, and was composed of the following proportions

Disk  384            

Sphere 96

 Long  32

What is reason for F2 phenotype?
TLS Online TPP Program

#Question id: 4732

#Unit 8. Inheritance Biology

What is F2 phenotype ratio observed when a homozygous recessive mutation in either or both of two different genes results in the same mutant phenotype?
TLS Online TPP Program

#Question id: 4733

#Unit 8. Inheritance Biology

If a homozygous plant with red peppers is crossed with a homozygous plant with green peppers, all the F1 plants have red peppers. When the F1 are crossed with one another, the F2 are in a ratio of 9 red : 3 brown : 3 yellow : 1 green  due to
TLS Online TPP Program

#Question id: 4734

#Unit 8. Inheritance Biology

If a homozygous plant with red peppers is crossed with a homozygous plant with green peppers, all the F1 plants have red peppers When the F1 are crossed with one another then produced following progeny Which of following interaction involved in gene to gene of peppers plant?