Question

18.       Certain proteins are referred to as tumor suppressors because:

A.         when their function is increased they promote cell division

B.         when their function is decreased they inhibit cell division

C.        when their function is decreased, cell division can increase dramatically

D.        none of the above

Answer _________

19.       A protein whose normal function is to promote cell cycle arrest and/or apoptosis is most likely to function as a _____________during cancer.

A.         proto-oncogene

B.         oncogene

C.        tumor suppressor

D.        tumor activator

Answer _________

20.       Gain-of-function mutations in proto-oncogenes will drive a cell towards cancer:

A.         because proto-oncogenes code for proteins that promote cell division

B.         because proto-oncogenes code for proteins that promote apoptosis

C.        because proto-oncogenes code for proteins that inhibit cell division

D.        none of the above

Answer _________

21.       Hereditary retinoblastoma is more common than non-hereditary retinoblastoma because:

A.         people with the hereditary form of the disease already have one defective Rbgene when they     are born

B.         in non-hereditary retinoblastoma, it is much more likely that both copies of a person's Rb genes will become mutated and inactive

C.        Rbis an oncogene and thus is much more likely to be mutated when inherited

Answer _________

22.       The major components of a basal lamina are:

A.         type I collagen, laminin, and fibronectin

B.         type IV collagen, laminin, nidogen, and heparan sulfate

C.        type IX collagen, laminin, and nidogen

D.        type IV collagen, laminin, nidogen, and perlecan

Answer _________

23.       The plus ends of actin and microtubule filaments are more dynamic than the minus ends because:

A.         it is the end that is anchored to the microtubule-organizing center

B.         it is the end where the rates of both growth and shrinkage are fastest

C.        it is the end used preferentially by intracellular vesicles

Answer _________

             

Answer 1

18. C

A tumor suppressor gene or anti-oncogene is a gene that regulates a cell during cell division and replication.

If the cell grows uncontrollably, it will result in cancer. When a tumor suppressor gene is mutated then it results in a loss or reduction in its function in combination with other genetic mutations this could allow the cell to grow abnormally.

The loss of function for these genes may be even more significant in the development of human cancers compared to the activation of oncogenes.

19. B

oncogene whose encoded oncoprotein provides an excessive or uncontrolled growth-promoting signal.

Because most proto-oncogenes are basic to animal life, they have been highly conserved over eons of evolutionary time.

p53 can promote apoptosis, cell-cycle arrest and senescence such that loss of p53 function increases viability, chromosomal instability and cellular lifespan. The apoptotic activity is important in tumor suppression.

P53 forms a homotetrameric transcription factor that is reported to directly regulate ~500 target genes, thereby controlling a broad range of cellular processes, including cell cycle arrest, cell senescence, DNA repair, metabolic adaptation and cell death.

20. A

A proto-oncogene is a normal gene found in the cell. There are many proto-oncogenes.

Each one is responsible for making a protein involved in cell growth, division and other processes in the cell.

The two mechanisms generate oncogenes whose protein products are identical with the normal proteins.

Their oncogenic effect is due to their being expressed at higher-than-normal levels or in cells where they normally are not expressed.

The arise or gain-of-function mutations that convert proto-oncogenes to oncogenes act dominantly, that is mutation in only one of the two alleles is sufficient for induction of cancer.

21. C

The other two-thirds of retinoblastomas are non-hereditary, which means that RB1 gene mutations are present only in cells of the eye and cannot be passed to the next generation.

In hereditary retinoblastoma mutations in the RB1 gene appear to be inherited in an autosomal dominant pattern.

The chain of events inside cells that leads to retinoblastoma is complex but it almost always starts with a change (mutation) in the RB1 gene.

The normal RB1 gene helps keep cells from growing out of control but a change in the gene stops it from working.

Depending on when and where the change in the RB1 gene occurs, it can result in 2 different types of retinoblastoma.