1. What is a sarcoma?

A sarcoma is a malignant tumor that originates from connective or other non-epithelial tissue. This means it is a cancer that starts in tissues such as cartilage, adipose tissue, bone, or muscle, which are all types of connective tissue.

2. Provide two examples of sarcomas mentioned in the text and their typical locations.

Ewing sarcoma is typically observed in the bone tissue of children and teenagers. Kaposi sarcoma develops from cells covering blood vessels or lymph vessels.

3. Besides sarcoma, what are some other special names for malignant tumors mentioned, and what do they indicate?

Other special names include leukemia, lymphoma, or neuroblastoma. Each of these names indicates a specific origin and characteristic of the malignant tumor, helping to classify them based on their tissue of origin.

4. What are the three critical gene groups whose alterations typically lead to cancer development?

Cancer typically arises due to genetic and epigenetic alterations affecting three critical gene groups: oncogenes, tumor suppressor genes, and DNA repair genes. These alterations disrupt normal cellular processes, leading to uncontrolled growth.

5. Define oncogenes and explain their role in cancer cells.

Oncogenes are localized cancer genes found within chromosomes that have been identified in various tumors. They are the primary factors that initiate uncontrolled proliferation in cancer cells, driving their rapid and unregulated growth by promoting cell division.

6. How are oncogenes related to proto-oncogenes?

Oncogenes are, in fact, mutant forms of what are known as proto-oncogenes. These proto-oncogenes become either overexpressed or activated through mutations, transforming into oncogenes that promote cancerous growth.

7. What is the normal function of proto-oncogenes in a healthy cell?

Normally, proto-oncogenes are crucial for regular cellular replication and the positive control of cell division. They play vital roles in maintaining normal cellular processes, ensuring cells grow and divide appropriately.

8. Name the five groups of proto-oncogenes based on their function in regulating the cell cycle and cell division.

The five groups of proto-oncogenes are growth factors, growth factor receptors, signal transmitters, transcription factors, and apoptosis regulators. All these play vital roles in maintaining normal cellular processes and cell cycle control.

9. Describe the primary role of tumor suppressor genes.

Tumor suppressor genes function in direct opposition to oncogenes. Their primary role is to suppress growth signals, thereby protecting cells against DNA damage and preventing uncontrolled cell division.

10. How do tumor suppressor genes protect cells against DNA damage and prevent the spread of mutations?

They actively participate in DNA repair mechanisms and are responsible for halting the cell cycle to guide damaged cells towards apoptosis, or programmed cell death. This ensures that cells with potentially harmful mutations do not continue to divide and proliferate.

11. What is the function of DNA repair genes?

DNA repair genes are specialized genes that detect DNA damage and resolve it by performing various repair processes. These processes include base and nucleotide removal repairs, mismatch repairs, and recombinational repair, maintaining genomic integrity.

12. What happens if DNA repair genes become inactivated through mutations?

If DNA repair genes become inactivated through mutations, the frequency of other mutations will significantly increase. This includes mutations that convert proto-oncogenes into active oncogenes and those that inactivate tumor suppressor genes, further contributing to cancer development.

13. List the four categories of external factors that play a significant role in the activation of cancer genes.

The external factors that activate cancer genes include somatic mutations, physical factors (primarily radiation), chemical factors (often referred to as chemical mutagens), and various types of viruses.

14. What are somatic mutations in the context of cancer gene activation?

Somatic mutations are acquired genetic changes that occur in non-germline cells. These mutations are not inherited but can contribute to the development of cancer by altering genes like oncogenes or tumor suppressor genes, leading to abnormal cell behavior.

15. What percentage of all cancers globally are estimated to be linked to viral infections?

Viruses are responsible for an estimated 15 to 20 percent of all cancers globally. This highlights their significant role as an external factor in cancer development, influencing a substantial portion of cases worldwide.

16. Name two examples of cancers linked to viral infections mentioned in the text.

Examples of cancers linked to viral infections include hepatocarcinoma, cervix cancer, Burkitt lymphoma, and Kaposi sarcoma. These demonstrate the diverse range of cancers that can be influenced by viral agents.

17. What are the two main types of tumor viruses based on their genome? Provide an example for each.

Tumor viruses can possess either a DNA genome, such as papilloma and adenoviruses, or an RNA genome, exemplified by retroviruses like HIV. Their genomic structure dictates their replication and integration mechanisms.

18. Explain the first mechanism, transduction, by which retroviruses contribute to cancer.

In transduction, retroviruses integrate into the host's genome. When they subsequently leave the host cell, they inadvertently copy a mutant oncogene along with their own genetic material. Thus, these viruses carry oncogenes with them when they infect another cell, transferring the cancer-promoting genes.

19. Explain the second mechanism, transcription, by which retroviruses contribute to cancer.

In transcription, when the virus integrates into the host genome, it inserts specific regions called LTRs (Long Terminal Repeats), which are present in its own genome, into a silent proto-oncogene within the host cell. This insertion then activates the proto-oncogene, transforming it into an oncogene.

20. According to the World Health Organization, what was the global impact of cancer in 2018 regarding deaths and new cases?

According to the World Health Organization, cancer was the second leading cause of death globally in 2018, responsible for an estimated 9.6 million deaths. Approximately 14 million new cancer cases were diagnosed each year, highlighting its widespread impact.

21. List three of the most common cancers by incidence mentioned in the text.

The most common cancers by incidence include lung, breast, colorectal, prostate, non-melanoma skin cancer, and stomach cancer. These represent a significant portion of newly diagnosed cancer cases worldwide.

22. Name three of the leading causes of cancer death globally.

The leading causes of cancer death globally are lung, colorectal, stomach, liver, and breast cancers. These cancers contribute to a large number of fatalities despite advances in treatment.

23. What are the most common cancers in men, and what are two diagnostic methods for prostate cancer?

In men, the most common cancers are lung, prostate, colorectum, stomach, and liver. Diagnostic methods for prostate cancer include the digital rectal exam, where a doctor manually examines the prostate, and the Prostate-Specific Antigen (PSA) test, a blood test for PSA levels.

24. What are the most common cancers in women?

In women, the most common cancers are breast, colorectum, lung, cervix, and stomach. These cancers represent a significant health burden for the female population globally.

25. List three preventable behavioral and dietary risk factors linked to cancer deaths.

Preventable behavioral and dietary risk factors linked to cancer deaths include a high body mass index, low fruit and vegetable consumption, lack of physical activity, tobacco usage, and alcohol consumption. Modifying these factors can significantly reduce cancer risk.