Question

1. Describe where embryonic and adult (somatic) stem cells are found. Compare and contrast the differentiation potential of adult and embryonic stem cells. Now, explain why embryonic stem cells may have greater therapeutic potential than adult stem cells. Explain why the use of embryonic stem cells is controversial. Outline somatic cell nuclear transplantation (SCNT) and describe the two possible outcomes of the process. Describe induction of stem cells. Finally, discuss the significance of induced pluripotent stem cells from both scientific and ethical standpoints.

2. List and describe four mechanisms for reducing your risk of becoming infected by antibiotic-resistant bacteria. Define “gene pool.” Next, relate evolution to gene pool and allele frequencies.

Answer 1

1. A) Embryonic stem cells are derived from very early embryos called blastocysts. They are found in the inner cell mass of a blastocyst.

Adult stem cells have been identified in many organs and tissues including brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian epithelium and testis. They are thought to reside in a specific area of each tissue called a 'stem cell niche'.

B) Embryonic stem cells have greater differentiation potential than adult stem cells because embryonic stem cells can develop into almost every type of cell in the human body, while adult stem cells may only develop into a limited number of cell types.

Embryonic stem cells are capable of almost unlimited division or proliferation when placed in a culture whereas adult stem cells do not multiply so readily.

Embryonic stem cells can be grown easily in the laboratory whereas adult stem cells are not easily grown after isolation from mature adult tissues.

C) Because of their unlimited differentiation potential, embryonic stem cells may provide a long term source of progenitor cells to replace the tissue lost in chronic disease. These cells could be differentiated into any cell type to treat degenerative, malignant or genetic diseases or injury due to inflammation, infection and trauma (For e.g. Alzheimer's, Parkinson's disease, diabetes, heart failure, bone marrow failure)

D) Most of the controversy rests on the fact that destruction of embryos occurs when stem cells are derived. The removal of inner cell mass prevents the blastocyst from continuing to develop. And the controversy is centered on the moral implications of destroying human embryos.

E) Somatic cell nuclear transplantation(SCNT) is a technique for cloning. In this process a donor nucleus is implanted into a healthy enucleated egg or oocyte. The resulting embryo can be used to generate embryonic stem cells or can be implanted into a surrogate mother to create a cloned individual, such as Dolly the sheep.

F) Induction of stem cells involves genetically reprogramming adult cells to an embryonic stem cell-like state. This is by introducing genes and factors important for maintaining the essential properties of embryonic stem cells.

G) Induced pluripotent stem cells can be used as a tool for drug development, modelling of disease and transplantation medicine.

2. Antibiotics should be used only when necessary. Never take antibiotics in viral infections.

Infection can be prevented by practising proper hand hygiene and sanitation methods. Antibiotic resistance can also be prevented through immunization.

Gene pool refers to the total number of genes of every individual in a population. In other words, it can be defined as the sum total of genes with all their variations possessed by a particular species at a particular time.