Question

Which ONE of the following is NOT TRUE about noncoding RNAs:

		microRNAs (~22 nucleotides long) regulate gene expression via RNA degradation
		microRNAs regulate genes expression via inhibition of translation
		microRNAs are encoded as genes in the human genome and can act as either oncogenes or tumor suppressor genes
		long non coding RNAs (lncRNAs) are 20,000+ nucleotides long

QUESTION 2

Which ONE of the following is NOT a method by which a tumor suppressor gene can lead to cancer:

		incorporation into a retroviral genome
		none of the answers (i.e., all of the other answers are true)
		chromosomal deletion of the gene
		loss of heterozygosity by non disjunction
		methylation of the promoter of the tumor suppressor gene

QUESTION 3

Which ONE of the following is NOT TRUE about retroviruses:

they cause tumors in animals, but not humans

retroviruses pick up cellular genes and alter them into constitutively active forms

cellular oncogenes in humans were identified using v-onc genes as probes in Western blot analysis

comparison of acutely transforming to non transforming viruses helped identify viral oncogenes

retroviruses have RNA genomes

QUESTION 4

1. Which ONE of the following is NOT TRUE about the TGF-beta pathway:

Involves a tyrosine kinase receptor

Turns on the expression of cyclin-dependent kinase inhibitor genes

Activates cytoplasmic transcription factors called SMADs

None of the answers (i.e., all of the other answers are true)

Induces cells to differentiate

QUESTION 5

1. Which ONE of the following does NOT activate the expression of cyclin genes:

		E2F
		AP1 (Fos/Jun)
		p53
		NFkB
		c-Myc

  

QUESTION 6

1. Which ONE of the following is NOT TRUE about the ubiquitin pathway:

there are relatively few E3 ubiquitin ligase genes but many E1 and E2 genes

The Ubiquitin pathway plays an important role in regulating the level of proteins in a cell

E3 ubiquitin ligase attaches ubiquitin to proteins as a signal for degradation by the proteasome

Ubiquitin is a 76-amino acid polypeptide encoded in the genome

Myc, IkB and p53 are all targets of ubiquitination

QUESTION 7

1. Which ONE of the following is NOT TRUE about Src:

		the viral form (v-Src) is constitutively active due to its SH2 domain binding phosphoTry527
		one of its substrates is cortactin which binds actin and promotes actin polymerization
		it was first identified in a virus that causes tumors in chickens
		the cellular form (c-Src) can be activated by its SH3 domain binding proline rich regions (Pro-X-X-Pro) in other proteins
		it is a tyrosine kinase

QUESTION 8

1. Which ONE of the following is NOT TRUE about p16:

		it is an oncogene
		it is on the same pathway and hence seldom mutated in tumors when RB is
		it is often mutated in cancers such as familial melanoma
		it is encoded in the same gene locus as p19-ARF
		It is a cyclin dependent kinase inhibitor (CKI)

QUESTION 9

1. Which ONE of the following is NOT a property of the transformed phenotype:

		Induced by over expression of tumor suppressor genes
		Anchorage independence
		Infinite proliferative life span
		Lower requirement for growth factors
		Does not exhibit density-dependent inhibition of cell growth

  

Answer 1

Answer 1:

DNA is transcribed into RNA by the process of transcription. The transcribed RNA can be coding or non-coding. The coding RNA is used as a template for production of proteins, but non-coding RNA is not translated into proteins. The non-coding RNA (nc RNA) acts as regulatory molecules in the cell. ncRNA is of various types, and broadly divided into small nc RNA and long nc RNA.

ncRNA regulates transcriptions, as wells as translation. The long ncRNA are of sizes larger than 200 nucleotides. However, they are not oncogenes or tumor supressor genes. The correct choice should be:

(C) microRNAs are encoded as genes in the human genome and can act as either oncogenes or tumor suppressor genes