(a) Write the characteristics of 'stem cells'.

(b) From where can one obtain in humans ?

(c) State any two applications of stem cells in curing human diseases.

The correct answer is:

(a) They have the ability of self-renewal / to divide, and differentiate into any kind of cell/tissue/organ.
(b) Inner cell mass of blastocyst / umbilical cord / Bone marrow.
(c) Diabetes treatment via forming islets of Langerhans, Restoration of vision by injecting stem cells, to treat rheumatoid arthritis, reduces pancreatic cancer, to treat genetic disorder like cystic fibrosis, spinal cord injuries, heart disease, any other correct application.

Detailed Step-by-Step Explanation:

(a) Characteristics of Stem Cells:
Stem cells are unique, unspecialized biological cells that possess two defining characteristics:
1. Self-Renewal: They have the capability to go through numerous cycles of cell division (mitosis) while maintaining an undifferentiated state.
2. Potency/Differentiation: They have the potential to differentiate into specialized cell types, such as muscle cells, blood cells, or brain cells, which can form tissues and organs.

(b) Sources of Stem Cells in Humans:
In humans, stem cells can be harvested from several sources depending on the developmental stage:
1. Inner Cell Mass of Blastocyst: Embryonic stem cells are obtained from the inner cell mass of an early-stage embryo (blastocyst). These are pluripotent, meaning they can form almost any cell type in the body.
2. Umbilical Cord: Cord blood stem cells can be collected from the umbilical cord immediately after birth. These are rich in hematopoietic (blood-forming) stem cells.
3. Bone Marrow: Adult stem cells (such as hematopoietic stem cells and mesenchymal stem cells) are found in bone marrow and are primarily responsible for replacing damaged cells throughout a person's life.

(c) Applications of Stem Cells in Curing Human Diseases:
Stem cells can be used in regenerative medicine to replace or repair damaged tissues and organs. Key applications include:
1. Diabetes Treatment: Culturing stem cells to differentiate into functional islets of Langerhans (insulin-producing cells) to restore blood glucose regulation in diabetic patients.
2. Restoration of Vision: Injecting stem cells to repair or replace damaged retinal cells, helping to restore sight.
3. Other Therapeutic Uses: Treating autoimmune disorders like rheumatoid arthritis, reducing pancreatic cancer progression, correcting genetic disorders such as cystic fibrosis, and repairing damaged tissues in spinal cord injuries or heart diseases.