TLS Online TPP Program

#Question id: 5655


What is the "acrosomal reaction"?

#Unit 5. Developmental Biology
  1. The acrosomal reaction is a repulsive interaction between the sperm and the egg.

  2. The acrosomal reaction is the digestion of the acrosome by the sperm when it encounters an egg.

  3. The acrosomal reaction is the digestion of the zona pellucida, permitting the sperm to contact the egg.

  4. The acrosomal reaction is the fusion of the sperm and egg plasma membranes.

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TLS Online TPP Program

#Question id: 1384

#Unit 4. Cell Communication and Cell Signaling

Mutations that block expression of the E-cadherin gene are thought to be an important step in metastasis. To better understand how loss of E-cadherin contributes to metastasis, scientists created two cell lines that differed in their expression of E-cadherin. One cell line expressed normal E-cadherin, but at 10% of the usual levels. The other cell line expressed normal E-cadherin at the usual levels, and also, at high levels a mutant form that included the cytoplasmic domain but lacked the rest of the protein. Both cell lines exhibited strongly reduced cell adhesion in culture. However, only the cell line with reduced expression of normal E-cadherin metastasized when introduced into mice.

Which of the following hypotheses is most consistent with the observations on cell adhesion and metastasis in these cell lines?

TLS Online TPP Program

#Question id: 19562

#Unit 12. Applied Biology

It has been suggested that interaction of the toxin fragment with the receptor facilitates proteolytic removal of toxin a helix, which triggers toxin oligomerization that leads to 

TLS Online TPP Program

#Question id: 33282

#Unit 2. Cellular Organization

The completion of a normal anaphase depends on the dephosphorylation of Cdk substrates, which in most cells results from the:

TLS Online TPP Program

#Question id: 15458

#Unit 2. Cellular Organization

In nature, bacteria

TLS Online TPP Program

#Question id: 3672

#Unit 3. Fundamental Processes

During initiation of replication