Chapter 12

BRCA1/BRCA2

human genes that produce tumor suppressor proteins. These proteins help repair damaged DNA and, therefore, play a role in ensuring the stability of the cell's genetic material. two major breast cancer susceptibility genes-cause double stranded breaks in DNA and prevents the fixing of DNA which will lead to uncontrolled cell growth

What is the difference between a proto-oncogene and an oncogene? What processes or events can cause a proto-oncogene to become an oncogene?

-In cancerous cells, mutant proto-oncogenes are often switched on permanently or overproduce their products; therefore cells receive constant internal signals to keep dividing, and uncontrolled cell division results. Mutant forms of proto-oncogenes are called oncogenes (def: genes that induce or continue uncontrolled cell proliferation). -Proto-oncogenes are just normal genes that initiate or maintain cell division that may become cancer genes by mutation.

Dedifferentiation

A cellular process in which a differentiated cell loses its special form or function, or reverts to an earlier developmental stage

translocation

transfer of part of a chromosome to a different position especially on a nonhomologous chromosome; especially : the exchange of parts between nonhomologous chromosomes

Chromosome rearrangement

type of chromosome abnormality involving a change in the structure of the native chromosome. Such changes may involve several different classes of events, like deletions, duplications, inversions, and translocations.

Angiogenesis

when blood vessels attach to a tumor and provide it with oxygen→ if this oxygen is taken away, the tumor can't survive

What is the evidence that some cancers might be caused by the environment, rather than being inherited? What are some of the environmental causes of cancer? What are the potential mechanisms by which these environmental factors contribute to cancer risk?

The Cancer genome atlas and research in epigenetics. SOME CAUSES: Certain viruses, radiation, chemicals, infections, as well as lifestyle choices and behaviors such as diet, sun exposure, and tobacco. Analysis of the patterns of DNA methylation are used to distinguish invasive from noninvasive forms of cancer and to diagnose subtypes. Resistance can develop based on these environmental factors.

Tumor suppressor gene

genes encoding proteins that suppress cell division

Explain why chromosomal rearrangements like translocations can create cancer- causing genes, and describe one specific example.

One of the best-established links between cancer and chromosomal aberration is a translocation between chromosome 9 and chromosome 22 in chronic myelogenous leukemia. (Originally called Philadelphia chromosome) (LOOK AT TABLE 12.6) the C-ABL gene on chromosome 9 is combined with part of the BCR gene on chromosome 22 to form a hybrid gene. The normal BCR allele encodes a protein that switches other proteins on or off by adding phosphate groups to them. BCR target proteins control gene expression and cell growth. Hybrid gene encodes a unique protein that constantly signals the white blood cell to divide, even in the absence of external signals.

Oncogene

genes that induce or continue uncontrolled cell proliferation

Compare and contrast how mutations in an oncogene or in a tumor suppressor can lead to cancer.

Tumor suppressor genes decrease cell division. Oncogenes cause increased cell division. If uncontrolled cellular division occurs, mutated cells will pass through the cell cycle more quickly, and will likely bypass cell checkpoints that would've corrected the error.

Loss of heterozygosity

a gross chromosomal event that results in loss of the entire gene and the surrounding chromosomal region. --in a cell, the loss of normal function in one allele of a gene where the other allele is already inactivated by mutation

Carcinogen

a substance capable of causing cancer in living tissue.

Explain what is meant by the following statements: a. "No one ever inherits cancer; what's inherited is the predisposition to certain sorts of cancer." b. "Just because you don't have a family history doesn't mean you won't get cancer."

a. "No one ever inherits cancer; what's inherited is the predisposition to certain sorts of cancer." -Cancer itself isn't heritable, however you can inherit genetic predispositions that make it more likely for you to develop cancer. Certain genes may cause a higher risk, and can cause cancer when combined with environmental agents. - A predisposition to more than 50 forms of cancer is inherited to one degree or another. b. "Just because you don't have a family history doesn't mean you won't get cancer." -Environmental factors (such as chemicals, toxins, sunlight, smoking, etc.) can cause cancer -Mutations are the number one cause of cancer, and can occur throughout one's life when exposed to mutagens or as age increases.

Philadelphia chromosome

an abnormal small chromosome sometimes found in the leukocytes of leukemia patients.

Cancer stem cell

cancer cells (found within tumors or hematological cancers) that possess characteristics associated with normal stem cells, specifically the ability to give rise to all cell types found in a particular cancer sample.

Metastasis

cells break away from the original cancer tissue and move to other parts of the body, starting new tumors in new tissues

DNA Repair

collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome.

Proto-oncogene

normal genes that initiate or maintain cell division that may become cancer genes (oncogenes) by mutation