According to the Switching mechanism, monomeric G proteins exist in two states. Match the following states (Column I) with correct mechanism (Column II).

Column I	Column II
A. “ON” state	i. switch I and switch II, are bound to the terminal γ phosphate of GTP through interactions with the backbone amide groups of conserved threonine and glycine residues.
B. “OFF” state	ii. GTPase-activating proteins
	iii. guanine nucleotide exchange factor
	iv. Due to the removal of the γ phosphate by GTPase-catalyzed hydrolysis causes switch I and switch II to relax into a different conformation

#Question id: 8720

#Unit 9. Diversity of Life Forms

The question refers to the following table, which compares the percent sequence homology of four different parts (two introns and two exons) of a gene that is found in five different eukaryotic species. Each part is numbered to indicate its distance from the promoter (for example, Intron I is the one closest to the promoter). The data reported for species A were obtained by comparing DNA from one member of species A to another member of species A.

Which of these four gene parts should allow the construction of the most accurate phylogenetic tree, assuming that this is the only part of the gene that has acted as a reliable molecular clock?

#Question id: 8721

#Unit 9. Diversity of Life Forms

Based on cladistics, which eukaryotic kingdom is polyphyletic and, therefore, unacceptable?

#Question id: 8773

#Unit 9. Diversity of Life Forms

Which eukaryotic kingdom includes members that are the result of endosymbioses that included an ancient aerobic bacterium and an ancient cyanobacterium?

#Question id: 8774

#Unit 9. Diversity of Life Forms

A large proportion of archaeans are extremophiles, so called because they inhabit extreme environments with high acidity, salinity, and/or temperature. Such environments are thought to have been much more common on primitive Earth. Thus, modern extremophiles survive only in places that their ancestors became adapted to long ago. Which of the following is, consequently, a valid statement about modern extremophiles, assuming that their habitats have remained relatively unchanged?

#Question id: 8775

#Unit 9. Diversity of Life Forms

Use the following information to answer the question. Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "chromatophores." The chromatophores are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants. A crucial photosynthetic gene of the cyanobacterium that gave rise to the chromatophore is called psaE. This gene is present in the nuclear genome of the cercozoan, but is not in the genome of the chromatophore. This is evidence of ________.

#Question id: 8776

#Unit 9. Diversity of Life Forms

What kind of evidence has recently made it necessary to assign the prokaryotes to either of two different domains, rather than assigning all prokaryotes to the same kingdom?