6.4 - Issues of Cell Division on Human Health

Cancer is a disease as a result of uncontrolled mitosis. Uncontrolled mitosis can be due to severe disruption and mechanism that controls the cell cycle. Tumor will form if cancer cells continue to divide uncontrollably and not destroyed. Tumor can be divided into:

• Benign tumor, which is mild, not aggressive and can be removed surgically.
• Malignant tumor, also called cancer, is a more dangerous and life-threatening type

Other factors such as ionizing radiations (X-rays, UV rays, gamma rays), chemical compounds (tar in tobacco smoke), carcinogenic substances (formaldehyde), mutations and damage to the DNA can result in cancer formation.

Figure 22 - Normal cells (left) have uniform shapes while tumor cells (right) are irregular in shape due to abnormal growth.

Abnormalities during meiosis can also result in genetic diseases. One most commonly known example is Down syndrome. Down syndrome patients have 47 chromosomes in total. During anaphase I or II, the spindle fibres fail to function which results in the failure of the chromosome to separate.

Figure 23 - Down syndrome is also known as trisomy 21 due to the extra copy of chromosomes at chromosome 21.