Use the Following Information When Answering the Corresponding Questions)

question 28

Multiple Choice

Use the following information when answering the corresponding questions) .
A group of enzymes known as cytosine- specific DNA methylases recognize CpG dinucleotide sequences-that is, a cytosine followed by a guanosine G) in one DNA strand-and add methyl groups to the cytosine. Many proteins bind to methylated CpG, including the methyl- CpG binding protein 2 MeCP2) . MeCP2 binding leads to the formation of a closed state of chromatin, thus silencing gene expression. A recent paper by Chen et al. reported an interesting mechanism of regulating transcription of a gene via MeCP2 W. Chen, Q. Chang, Y. Lin, A. Meissner, A. E. West, E. C. Griffith, R. Jaenish, and M. Greenberg. 2004. Derepression of BDNF transcription involves calcium- dependent phosphorylation of MeCP2, Science 302:885-89) . This gene, called BDNF, encodes brain- derived neurotrophic factor BDNF) -a protein that plays an important role in nerve cell and central nervous system function, including memory and learning. Remarkably, most cases of Rett syndrome, an important cause of mental retardation in females, are due to loss- of- function mutations of MeCP2.
-A patient is undergoing genetic screening for cancer. The results show the patient has many proto- oncogenes. Based on this information only, which of the following statements is correct regarding the probability that this patient will develop cancer in the very near future?

• A) The chances are low because the patient would have to show an increased number of oncogenes.
• B) The chances are high because the patient most likely also shows an increase in the number of tumor suppressors.
• C) Due to the increased number of proto- oncogenes, the chances are high.

---

Definitions:

Systematic Desensitization

A therapeutic technique used to reduce fear or anxiety, by gradually exposing the person to the feared object or context without any danger.

Exposure

A therapeutic technique where individuals confront their fears or traumatic memories in a safe and controlled environment to reduce their power.

Classical Conditioning

A learning process that occurs when two stimuli are repeatedly paired; a response that is at first elicited by the second stimulus is eventually elicited by the first stimulus alone.

Operant Conditioning

A method of learning that occurs through rewards and punishments for behavior.