Question

Apply Your Knowledge 16.1 e following questions focus on what you have just learned about various cancer cells and CRITICAL THINKING 1. What are oncogenes? 2. What are the four steps of the cell cycle? Explain them. 3. What are the warning signs of cancer in children? 4. Compare carcinoma with sarcomas. 5. In what stage of the cell cycle does DNA synthesis occur? 6. What is mitosis? Cancer Therapy and has the same life exp yidual. Complete respons

Answer 1

1. Oncogenes are cancer-causing or cancer-inducing genes that trigger cancer growth; transforms the infected cells so they divide out of control and form tumors

Some of the different categories of oncogenes include:

• Growth factors or mitogens – These oncogenes stimulate the growth, proliferation, and differentiation of cells. Growth factors are usually steroids or proteins secreted by cells to stimulate their own cell proliferation or the proliferation of other nearby or distant cells. These oncogenes can stimulate the cell to secrete growth factors when it would not normally do so, thereby inducing the cell’s abnormal proliferation. An example of an oncogene in this class is c-Sis.
• Receptor tyrosine kinases – Examples of oncogenes in this class include the epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), vascular endothelial growth factor receptor (VEGFR) and human epidermal growth factor receptor 2 (HER2/neu). The proteins encoded by these oncogenes are very important anti-cancer treatment targets.

2.Stages of the Cell Cycle

Cell cycle, the ordered sequence of events that occur in a cell in preparation for cell division. The cell cycle is a four-stage process in which :

i) the cell increases in size (gap 1, or G1, stage)

ii) copies its DNA(synthesis, or S, stage)

ii) prepares to divide (gap 2, or G2, stage)

iv) divides (mitosis, or M, stage).

The stages G1, S, and G2 make up interphase, which accounts for the span between cell divisions. On the basis of the stimulatory and inhibitory messages a cell receives, it “decides” whether or not it should enter the cell cycle and divide.

3.Warning signs of cancer in children

• An unusual lump or swelling
• Unexplained paleness and loss of energy
• Easy bruising
• An ongoing pain in one area of the body
• Limping
• Unexplained fever or illness that doesn’t go away
• Frequent headaches, often with vomiting
• Sudden eye or vision changes
• Sudden unexplained weight loss

4.Carcinoma :

• Arises from the epithelial cells
• Common sites include breast, prostate, lung, and colon
• Based on appearance and/or putative cell of origin
• The main route of spread for carcinomas is Lymph

Sarcoma :

• Arises from mesenchymal tissue (the connective or supportive tissue)
• Common sites include; bone, cartilage, fat, muscle, blood vessels
• The main route of spread for sarcomas is Blood

5.S-phase : (Synthesis phase) The period of DNA synthesis or replication.

During the interphase stage of the cell cycle, DNA replication occurs.

6. Mitosis

During this stage of the cell cycle, the sister chromatids separate and the nucleus divides in two or the part of the cell cycle during which the nucleus divides.

Mitosis, a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

Mitosis stages:

Prophase: The first step in mitosis where the cell's chromatin condenses into chromosomes.

Prometaphase: Nuclear membrane disintegrates, the centrioles reach the poles of the cell, and the chromosomes continue to contract.

Metaphase: Motor proteins pull sister chromatids to the cell's equator.

Anaphase: The chromatids of each chromosome separate at the centromere and move to opposite poles

Telophase: The nucleoli reappear, two new nuclear membranes begin to form, but the cell has not yet completely divided.