Cell Bio Unit 4

Which of the following is the term used to describe a thin, sheet-like meshwork of extracellular matrix components that can be found in epithelial tissues on which the epithelial cells are firmly attached?

Basal lamina

People with a defect in the synthesis of the integrin Beta2 subunit exhibit reduced:

Extravasation

Which of the following statements regarding gap junctions is false?

Human gap junctions are composed of proteins called innexins

Which of the following is not a role of tight junctions?

Rapid transmission of electrical signals between adjacent neurons

Desmosomes:

Contain the transmembrane proteins desmoglein and desmocollin

Which of the following is NOT a key step in the activation of leukocyte migration to the site of infection?

Induction of endothelial cell ICAM expression by leukocyte-secreted chemokines

Which statement BEST describes the structure of integrins?

Integrins are heterodimers composed of alpha and beta subunits

What signal is released by endothelial cells to recruit circulating leukocytes?

Vesicle-sequenced P-selectins are moved to the cell surface

Vertebrate gap junctions are composed of:

Connexins

Cadherin cellular adhesion molecules promote:

Cell-specific homophilic interactions

Which of the following statments best describes the difference between low-affinity integrins and high-affinity

Many integrins can exist in two conformations: a low-affinity (bent) conformation and a high-affinity (straight) conformation

Which of the following statements regarding cadherins is FALSE?

Cadherin diversity is expanded by the dimerization of distinct chain types

A tight junction is made up of which of the following proteins?

All of the answers are correct

The functions of the extracellular matrix include:

All of the answers are correct

The major families of cell surface adhesion molecules include:

All of the answers are correct

Which of the following statements correctly describes p53?

Activation of p53 leads to inhibition of the cyclin-CDK complexes

Hereditary cancers typically possess loss-of-heterozygosity in":

tumor-suppressor genes

A gain-of-function mutation in ________ will bypass restriction point

cyclin D

Which of the following is a tumor suppressor gene?

both p14ARF and Rb

Burkitt’s lymphoma results from the overproduction of:

Myc

Which of the following is the characteristic mutational cause for aberrants MYC activity in Burkitt’s lymphoma?

Translocation of the MYC oncogene to a region of highly active transcription

Which protein belongs to the control system that regulates cells past a certain point in late G1 (START)

both CDK4 and Rb

A bone tumor sample appears to be heterozygous for a p53. Which statement is the MOST likely explanation for this finding?

The p53 mutation is resulting in a dominant-negative p53 protein

Ras is a:

None of the answers is correct

In what way does the ras oncogene contribute to cancers?

ras codes for a GTPase, which in its mutated form cannot be switched off

The p53 protein is central to tumorigenesis, with the vast majority of human cancers having mutations in either p53 itself or in proteins that regulate p53. Which of the following is NOT a way in which defective regulation of p53 contributes to cancer?

The binding of MDM2 to p53 is prevented by hyperphosphorylation

Which of the following is NOT a mechanism for loss of heterozygosity?

Oncogene amplification

Which of the following is a characteristic of malignant tumors?

metastatic

Germ-line mutations in which of the following have been implicated in hereditary cancers?

All of the answer choices are correct

Which of the following is a proto-oncogene?

myc