12th Class Biology Microbes in Human Welfare Types of Diseases

The diseases may be broadly classified into two types : Congenital and acquired.

(1) Congenital Diseases : These are anatomical or physiological abnormalities present from birth. They may be caused by (a) a single gene mutation (alkaptonuria, phenylketonuria, albinism, sickle-cell anaemia, haemophilia, colour blindness); (b) chromosomal aberrations (Down’s syndrome, Klinefelter’s syndrome, Turner’s syndrome); or (c) environmental factors (cleft palate, harelip). Unlike the gene-and chromosome-induced congenital defects, environmentally caused abnormalities are not transmitted to the children.

(2) Acquired Diseases : These diseases develop after birth. They are further of two types : communicable and non-communicable.

(i) Communicable (Infectious) Diseases : These diseases are caused by viruses, rickettsias, bacteria, fungi, protozoans and worms.

(ii) Noncommunicable (Noninfectious) Diseases : These diseases remain confined to the person who develops them and do not spread to others. The non-communicable diseases are of four kinds :

(a) Organic or Degenerative Diseases : These diseases are due to malfunctioning of some of the important organs, e.g, heart diseases, epilepsy. Heart diseases result from the abnormal working of some part of this vital organ. Epilepsy may result from abnormal pressure on regions of the brain.

(b) Deficiency Diseases : These diseases are produced by deficiency of nutrients, minerals, vitamins, and hormones, e.g., kwashiorkor, beri-beri, goitre, diabetes are just a few from a long list.

(c) Allergies : These diseases are caused when the body, which has become hypersensitive to certain foreign substance, comes in contact with that substance. Hay fever is an allergic disease.

(d) Cancer : This is caused by a uncontrolled growth of certain tissues in the body.