TLS Online TPP Program

#Question id: 12186


In 2001, the Nobel Prize in Physiology or Medicine was awarded to three cell cycle scientists. Paul Nurse was recognized for his studies with the fission yeast S. pombe, in particular for the discovery and characterization of the wee1+ gene. What did the characterization of the wee1+ gene tell us about cell cycle control?

#Unit 2. Cellular Organization
  1. The dual-specificity protein kinase Wee1 phosphorylates CDKs on the activatory tyrosine 15.
  2. Yeast cells with a defective wee1+ gene activate S phase CDKs prematurely and hence experience premature entry into DNA replication. 
  3. Fission yeast cells carrying a CDK1 mutation in which the tyrosine 15 residue is replaced by phenylalanine (which is structurally similar to tyrosine but cannot be phosphorylated) show the premature mitotic CDK activation and entry into mitosis.
  4. The dual-specificity protein phosphatase Wee1 dephosphorylates CDKs on the inhibitory tyrosine 15.

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TLS Online TPP Program

#Question id: 8292

#Unit 9. Diversity of Life Forms

Some molecular data place the giant panda in the bear family (Ursidae) but place the lesser panda in the raccoon family (Procyonidae). If the molecular data best reflect the evolutionary history of these two groups, then the morphological similarities of these two species is most likely due to ________.

TLS Online TPP Program

#Question id: 8293

#Unit 9. Diversity of Life Forms

The importance of computers and of computer software to modern systematics s is most closely linked to advances in ________.

TLS Online TPP Program

#Question id: 8294

#Unit 9. Diversity of Life Forms

The common ancestors of birds and mammals were very early (stem) reptiles, which almost certainly possessed three-chambered hearts (two atria, one ventricle). Birds and mammals, however, are alike in having four-chambered hearts (two atria, two ventricles). The fourchambered hearts of birds and mammals are best described as ________.

TLS Online TPP Program

#Question id: 8295

#Unit 9. Diversity of Life Forms

Imagine that a phylogeny was developed for a group of mammals based on bone structure. Which of the following statements would be a reasonable prediction about a phylogeny for the same group of species based on similarities and differences in the structure of a particular enzyme?

TLS Online TPP Program

#Question id: 8296

#Unit 9. Diversity of Life Forms

Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species.


According to the phylogenetic tree in the figure above, G. intestinalis constitutes a ________ group.

TLS Online TPP Program

#Question id: 8680

#Unit 9. Diversity of Life Forms

Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species


By examining the phylogenetic tree diagrammed in the figure above, what conclusion can you draw about the species G. microti?