In E. coli, the five contiguoustrp genes encode enzymes that sythesize the amino acid tryptophan. These genes are expressed efficiently only when tryptophan is limiting. The genes are controlled by a repressor, just as the lac genes are, although in this case, it is the absence of its ligand (tryptophan) that relieves repression, match trp genes to their gene product,

Trp genes	Gene products
trpE	anthranilate synthetase
trpD	phosphoribosyl anthranilate transferase
trpC	phosphoribosyl anthranilate isomerase-indole glycerol phosphate synthetase
trpB	tryptophan synthetase beta
trpA	tryptophan synthetase alpha

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#Question id: 5009

#Unit 11. Evolution and Behavior

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped to make possible the evolution of the tetrapod limb. This type of change is illustrative of

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#Question id: 5010

#Unit 11. Evolution and Behavior

Which of the following steps has not yet been accomplished by scientists studying the origin of life? 

TLS Online TPP Program

#Question id: 5011

#Unit 11. Evolution and Behavior

A swim bladder is a gas-filled sac that helps fish maintain buoyancy. The evolution of the swim bladder from lungs of an ancestral fish is an example of

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#Question id: 5012

#Unit 11. Evolution and Behavior

A	Silurian	I	Seed plants appear
B	Devonian	II	Gymnosperms dominant
C	Carboniferous	III	Invasion of land by primitive land plants
D	Jurassic	IV	first reptiles

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#Question id: 5013

#Unit 11. Evolution and Behavior

Following is correct match

Periods	Age of evolutionary event
A- Jurassic	I- Fish
B- Ordovician	II- Amphibian
C- Devonian	III- Gymnosperm
D-Carbonyferous	IV- Invertebrates

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#Question id: 5014

#Unit 11. Evolution and Behavior

 Following geological time period and major evolutionary event?

I. Devonian                            A. Gymnosperms dominant

II. Jurassic                               B. Amphibians diversify; first reptiles

III. Carboniferous                  C. Mammals appear

IV. Triassic                           D. Seed plants appear