Genes that control coat color in mammals represent some of the best early examples of genes with multiple alleles exhibiting different phenotypes. A classic example is the C gene in hamsters. Three of the known alleles of this gene are C, c^a and c^k. Each supplies a different amount of black pigment to the coat hair. The phenotypes of three different homozygous strains are as follows.

would mate the true-breeding  c^a c^a  hamsters to the true-breeding c^k c^k  hamsters to produce heterozygous  c^a and c^k  F1 progeny. Crosses and their interpretation that would have allowed geneticists to come to the conclusion that c^a and c^k were likely to be alleles of the same using the concept that alleles of the same gene will be tightly linked. What will be the ratio of F2 hamster;

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#Question id: 13164

#Unit 4. Cell Communication and Cell Signaling

Match the following.

Column I	Column II	Column III
A. G Protein–Coupled Receptors That Activate PDE	i. cAMP	a. Increase in conversion of glycogen to glucose
B. G Protein–Coupled Receptors That Activate Adenylyl Cyclase	ii. cGMP	b. Hyperpolarization or depolarization of photoreceptor membrane
C. G Protein–Coupled Receptors That inhibit Adenylyl Cyclase	iii. DAG	c. activates genes necessary for cell division
D. G Protein–Coupled Receptors That Trigger Elevations in Cytosolic and Mitochondrial Calcium		d. increase in K+ permeability hyperpolarizes the membrane

Which one of the following is correct?

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#Question id: 13165

#Unit 5. Developmental Biology

One of the main ways by which the insulin signaling pathway might function to lower longevity is to activate mTORC1, a protein kinase complex that promotes the translation of mRNA into proteins in response to nutrients and hormones, select incorrect statement;

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#Question id: 13168

#Unit 10. Ecological Principles

Use the following diagram from the text showing the spread of the cattle egret, Bulbulcus ibis, since its arrival in the New World, to answer the following question.

How would an ecologist likely explain the expansion of the cattle egret?

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#Question id: 13169

#Unit 10. Ecological Principles

Which of the following causes Earth's seasons?

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#Question id: 13170

#Unit 10. Ecological Principles

Which of the following events might you predict to occur if the tilt of Earth's axis relative to its plane of orbit was increased 33.5 degrees?

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#Question id: 13171

#Unit 10. Ecological Principles

Imagine some cosmic catastrophe jolts Earth so that its axis is perpendicular to the orbital plane between Earth and the sun. The most obvious effect of this change would be