Chapter 11.7, Problem 1R

Summary Introduction

To review:

The comparison of cell morphology and genes function in the malignant and benign tumors, and normal tissues.

Introduction:

The uncontrolled cell growth leads to cancer, which is always associated with the formation of a mass of cells, called as tumors. The tumors, according to their property of metastasis and morphology, can be of two types: benign tumor and malignant tumor. The normal tissue is very much different with respect to the property of cells and gene regulation. The cells in the normal tissue are well regulated and they never evade the process of apoptosis.

Explanation of Solution

The comparison of genes function and cell morphology among the normal tissue, malignant tumor, and benign tumor is done on the basis of contact inhibition, metastasis, cell division, nucleus shape, apoptosis, and tumor-suppressor genes. The contact inhibition is the property of a cell to stop growing when it experiences contact with the other cells. It allows a cell to grow in a monolayer. Metastasis is the property of cells that get detached from the original mass and start a fresh growth at a new place.

Cell division is the property of a cell to get increased in number. Apoptosis is the normal regulated process that leads to the death of a damaged cell. The tumor-suppressor genes are the genes present at various cell-cycle checkpoints that do not allow the replication of mutated and damaged deoxyribonucleic acid (DNA). For example, p53 and Rb (retinoblastoma gene). Based on all these properties the comparison is tabulated as follows in Table 1.

Table 1: The comparison of cellular structure and function of genes among normal tissue, malignant tumor, and benign tumor.

Properties	Normal tissue cells	Malignant tumor cells	Benign tumor cells
Contact inhibition	Cells show the property of contact inhibition.	Cells lack the property of contact inhibition.	Cells lack the property of contact inhibition.
Metastasis	These cells lack the phenomenon of metastasis.	These cells show the phenomenon of metastasis.	These cells lack the phenomenon of metastasis.
Nucleus shape	The nucleus remains at the periphery according to cell and the cells show a uniform nucleus morphology.	The nucleus does not remain at the periphery according to cell and the cells show an irregular nucleus morphology.	The nucleus remains at the periphery according to cell and the cells show a uniform nucleus morphology.
Cell division	Cells divide according to the needs of concerned tissue.	Cells divide rapidly and they show the presence of high nucleus to cytoplasm ratio, a property of rapidly dividing cells.	Cells divide at a rate less than malignant tumor cells but more than the normal tissue cells.
Apoptosis	These cells undergo apoptosis by extrinsic and intrinsic factors.	These cells do not undergo the process of apoptosis.	These cells do not undergo the process of apoptosis.
Tumor-suppressor genes	These genes are present and activated when there is a presence of mutated or damaged DNA.	These genes are mutated.	These genes are mutated.

Conclusion

Therefore, it can be concluded that normal tissue has a presence of normal tumor-suppressor genes; on the other hand, the tumor cells have a mutated copy of the same. Normal cells show the property of contact inhibition, characteristic nucleus morphology, apoptosis, and regulated cell division. Malignant tumor cells show the property of metastasis, rapid cell growth, and evade apoptosis. The benign tumor lacks the property of metastasis, contact inhibition, and apoptosis but maintains a characteristic nucleus shape.