bio quiz 14

At which checkpoint may p53 initiate a process to halt cell division at this point if it senses DNA damage?

G1

Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. This information can now be utilized in breast cancer treatment if which of the following is true?

If the patient's cancer cells have detectable HER2.

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?

It interferes with rapidly dividing cells.

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

Why might a point mutation in DNA make a difference in the level of protein's activity?

It might substitute an amino acid in the active site.

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?

They cannot repair thymine dimers.

Breast tumor biopsy specimens can be typed for a number of gene expression patterns. Together, these can provide risk analysis for the likely aggressive growth and metastasis of the tumor. How can this most help the physician and patient?

This can help them to decide whether and what kind of chemotherapy is warranted.

In the 1920s Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals-she used nitrogen mustards-have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation?

We want to prevent any increase in mutation frequency.

Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?

a base deletion near the start of a gene

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

a base-pair deletion

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

For a particular microarray assay (DNA chip), cDNA has been made from the mRNAs of a dozen patients' breast tumor biopsies. The researchers will be looking for

a pattern shared among some or all of the samples that indicates gene expression differing from control samples.

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in

a polypeptide missing an amino acid.

Which of the following mutations is most likely to cause a phenotypic change?

a single nucleotide deletion in an exon coding for an active site

In which of the following ways could signal transduction most probably be explored in research to treat cancer?

alteration of protein kinases in cell cycle regulation in order to slow cancer growth

A frameshift mutation could result from

either an insertion or a deletion of a base.

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?

expression of inappropriate gene products

Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?

lack of appropriate cell death

Pharmacogenetics is an increasingly important discipline that uses genetic information to tailor the prescription of drug treatments to individuals. In the case of chemotherapy for breast cancer, for example, different patients need and/or respond to different treatments. Patients whose tumors are HER-2 positive respond to herceptin whereas other patients do not. Patients whose tumors have estrogen receptors will be best served if

the estrogen receptors are blocked by other molecules that can use the same receptors.

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?

translocation