* not completed

. Which of the following is believed to be a key cause of immortalization of cancer cells in many tumours?

Complete loss of telomeres. correct incorrect

Inactivation of the telomerase enzyme. correct incorrect

Reactivation of the telomerase enzyme. correct incorrect

Shortening of telomeres. correct incorrect

* not completed

. Which of the following best defines an oncogene?

An oncogene codes for a cell cycle control protein. correct incorrect

An oncogene codes for a mutated form of a protein that forms part of a signal transduction pathway. correct incorrect

An oncogene codes for a protein that prevents the cell from undergoing apoptosis. correct incorrect

An oncogene is a dominantly expressed mutated gene that gives a cell a growth or survival advantage. correct incorrect

* not completed

. Which of the following types of protein could be coded by a tumour-suppressor gene?

A protein that forms part of a growth factor signalling pathway. correct incorrect

A protein that codes for a DNA repair enzyme. correct incorrect

A protein that helps prevent apoptosis. correct incorrect

A protein that controls progression through the cell cycle. correct incorrect

* not completed

. In what way does the ras oncogene contribute to cancers?

Ras codes for an anti-apoptotic protein, which is produced in abnormally large amounts. correct incorrect

Ras codes for a GTPase switch protein, which in its mutated form cannot be switched off. correct incorrect

Ras codes for a transcription factor, which is produced in abnormally large amounts correct incorrect

Ras codes for a truncated form of a growth factor receptor, which is continually active. correct incorrect

* not completed

. Which property of p53 enables it to prevent the development of cancer?

p53 is a transcription factor that causes production of proteins that stimulate the cell cycle. correct incorrect

p53 prevents the replication of cells with damaged DNA. correct incorrect

p53 prevents cells from triggering apoptosis. correct incorrect

p53 stimulates synthesis of DNA repair enzymes that replace telomere sequence lost during cell division. correct incorrect

* not completed

. Which of the following statements about the Rb tumour suppressor protein is correct?

Rb is activated when phosphorylated by Cdk. correct incorrect

Rb binds the transcription factor E2F and thus prevents the cell from entering S phase until a mitogenic signal is received. correct incorrect

Rb is a transcription factor. correct incorrect

When a mitogenic signal is received, Rb binds the transcription factor E2F and thus stimulates the cell to enter S phase correct incorrect

* not completed

. Which of the following is a characteristic of a cancer cell? Please select all that apply.

Replicates an unlimited number of times. correct incorrect

Grows and divides without stimulation by a growth factor. correct incorrect

DNA damage does not halt cell division or stimulate apoptosis. correct incorrect

Releases factors which cause nearby cells to become cancerous. correct incorrect

* not completed

. Which of the following is characteristic of a malignant rather than a benign tumour?

Undergoes metastasis. correct incorrect

Develops a blood supply. correct incorrect

Cells divide an unlimited number of times. correct incorrect

Grows without needing a growth signal. correct incorrect

* not completed

. Which of the following types of mutation cannot give rise to an oncogene?

Addition or deletion of a base producing a nonsense message and an inactive protein product. correct incorrect

A point mutation changing just one amino acid in the protein product. correct incorrect

A translocation which puts the gene under the control of a strong promoter, producing over-expression. correct incorrect

A point mutation which produces a stop codon, prematurely terminating the message and producing a truncated protein. correct incorrect

* not completed

. Which of the following can cause mutations which contribute to development of cancers? Please select all that apply.

Chemicals in food. correct incorrect

UV and ionising radiation. correct incorrect

Reactive oxygen species. correct incorrect

HIV virus. correct incorrect

* not completed

. Both copies of a tumour suppressor gene must be inactivated by mutation in order to contribute to cancer development. True or false?

True correct incorrect

False correct incorrect

* not completed

. Which of the following types of reaction can be brought about in the detoxification processes catalysed by cytochrome P450?

Dehalogenations. correct incorrect

Hydroxylations. correct incorrect

Dephosphorylations. correct incorrect

Dehydrogenations. correct incorrect

* not completed

. Which of the following are possible mechanisms that can lead to the production of reactive oxygen species such as superoxide in cells?

A damaged and leaky mitochondrial inner membrane. correct incorrect

Mutations in mitochondrial DNA which might deflect electrons into reactive oxygen species. correct incorrect

Production of methaemoglobin from haemoglobin. correct incorrect

Ionising radiation. correct incorrect