STEM CELLS

What are the two main abilities of stem cells?

Self-renewal (make identical copies) and Differentiation (form specialised cells).

Why are stem cells important?

They replace dead or damaged cells, allowing growth, healing, and regeneration.

What are the main types of stem cells by potency?

Totipotent → Pluripotent → Multipotent → Fully differentiated.

What is the potency hierarchy pathway?

Totipotent → Pluripotent → Multipotent → Specialised cell.

What controls stem cell differentiation?

Gene expression via transcription factors and epigenetic changes (DNA methylation, histone modification).

What can totipotent cells form?

All body and placental cells (entire organism, e.g., fertilised egg).

What can pluripotent cells form?

Any body cell + supporting embryonic tissues (e.g., ESCs, iPSCs).

What can multipotent cells form?

Several related cell types (e.g., blood cells from bone marrow).

What can fully differentiated cells form?

Only their specific function (e.g., nerve, liver, or muscle cell).

Where are embryonic stem cells (ESCs) found?

In the inner cell mass (ICM) of the blastocyst (day 5 embryo).

What are the properties of ESCs?

Pluripotent, can grow indefinitely, form any cell type, used for therapy & research.

What are the challenges with ESCs?

Ethical issues, risk of tumour formation, and difficulty controlling differentiation.

Where are adult (tissue) stem cells found?

Bone marrow, brain, liver, skin, and umbilical cord.

What are adult stem cells used for?

Tissue repair and regeneration (multipotent).

What are induced pluripotent stem cells (iPSCs)?

Adult cells reprogrammed to act like embryonic stem cells.

Why are iPSCs important?

No ethical issues, no immune rejection, can become any cell type.

What are the disadvantages of iPSCs?

Possible genetic defects, mutation risk from viral insertion, some cancer-related genes used.

List 3 main applications of stem cells.

Research, drug testing, and cell therapy for disease treatment.

Give examples of diseases treated with stem cells in animal models.

Diabetes, Parkinson’s, spinal injury, heart damage, multiple sclerosis, immune deficiency.

What is the Tissue Renewal Principle?

Stem cells divide slowly and self-renew → progenitor cells divide rapidly → specialised cells perform function.

What ancient discovery showed early tissue repair knowledge?

Indian writings (\sim600 BC) describing skin grafts.

What 18th-century discovery revealed regeneration?

Hydra can regenerate (early regenerative biology).

What 19th-century concept introduced the term “stem cell”?

Fertilised egg as origin of all cells.

What early 1900s discoveries were key for stem cell theory?

• Cell culture methods (frog cells in lab) Blood stem cell theory (all blood cells from one ancestor cell) Belief nervous system can’t regenerate.

What mid-$1900$s discoveries shaped modern stem cell biology?

First cloning (nucleus holds full genome) Pluripotent cells in teratomas Bone marrow stem cells identified First bone marrow transplant.

What were the main 1980s milestones?

Mouse embryonic stem cells isolated Artificial skin made from patient’s own cells Knockout mice created (missing specific genes).

What were key 1990s discoveries?

Cancer stem cell concept Human embryonic stem cells isolated and cultured.

What was discovered in 2006?

iPSCs — adult cells reprogrammed into pluripotent stem cells.

What was achieved in 2010 and 2013?

2010: First human stem cell therapy 2013: Stem cells created via therapeutic cloning.

What was proven in 2016?

Reprogrammed skin cells can form new eggs → mice grown from skin cells.

What happens during Week 1 of embryonic development?

Fertilisation → cleavage → compaction → blastocyst formation → implantation.

What is cleavage?

Rapid mitotic divisions forming smaller cells (blastomeres).

What is compaction?

Cells tightly join via E-Cadherin → form a morula.

What is the blastocyst made of?

Inner Cell Mass (forms embryo) Trophoblast (forms placenta) Blastocoel (fluid cavity).

What happens during blastulation?

Embryo reaches the uterus at the blastocyst stage.

What are the 3 main parts of the blastocyst?

Inner Cell Mass, Trophoblast, and Blastocyst Cavity (blastocoel).

What are the two layers formed from the Inner Cell Mass?

Epiblast and Primitive Endoderm (Hypoblast).

What does the epiblast form?

The embryo.

What does the primitive endoderm form?

Extraembryonic tissues (like the yolk sac).

Which genes mark these layers?

Nanog (epiblast) and Gata6 (primitive endoderm).

What does the trophectoderm form?

Placenta and support tissues.

What happens during hatching?

Blastocyst breaks free from the zona pellucida (ZP).

What enzyme helps the blastocyst hatch?

Trypsin-like protease that lys

What is mitosis and growth in development?

Increase in cell number through mitotic division. Differential mitosis

→ not all cells divide at the same rate, driving tissue growth and organ formation.

What is restriction and determination?

Process where cells progressively lose totipotency: totipotent

→ pluripotent

→ multipotent

→ determined to a specific fate.

What is gene activation and differential expression?

Specific genes are turned on/off in different cells. Only genes needed for a cell

’s fate are expressed

→ differentiation.

What is differentiation? Give an example.

Process by which cells acquire a specific phenotype. Example: cytodifferentiation into muscle cells or neurons.

What are the two main abilities of stem cells?

Self-renewal (make identical copies) and Differentiation (form specialised cells).

Why are stem cells important?

They replace dead or damaged cells, allowing growth, healing, and regeneration.

What are the main types of stem cells by potency?

Totipotent

→ Pluripotent

→ Multipotent

→ Fully differentiated.

What is the potency hierarchy pathway?

Totipotent

→ Pluripotent

→ Multipotent

→ Specialised cell.

What controls stem cell differentiation?

Gene expression via transcription factors and epigenetic changes (DNA methylation, histone modification).

What can totipotent cells form?

All body and placental cells (entire organism, e.g., fertilised egg).

What can pluripotent cells form?

Any body cell + supporting embryonic tissues (e.g., ESCs, iPSCs).

What can multipotent cells form?

Several related cell types (e.g., blood cells from bone marrow).

What can fully differentiated cells form?

Only their specific function (e.g., nerve, liver, or muscle cell).

Where are embryonic stem cells (ESCs) found?

In the inner cell mass (ICM) of the blastocyst (day 5 embryo).

What are the properties of ESCs?

Pluripotent, can grow indefinitely, form any cell type, used for therapy & research.

What are the challenges with ESCs?

Ethical issues, risk of tumour formation, and difficulty controlling differentiation.

Where are adult (tissue) stem cells found?

Bone marrow, brain, liver, skin, and umbilical cord.

What are adult stem cells used for?

Tissue repair and regeneration (multipotent).

What are induced pluripotent stem cells (iPSCs)?

Adult cells reprogrammed to act like embryonic stem cells.

Why are iPSCs important?

No ethical issues, no immune rejection, can become any cell type.

What are the disadvantages of iPSCs?

Possible genetic defects, mutation risk from viral insertion, some cancer-related genes used.

List 3 main applications of stem cells.

Research, drug testing, and cell therapy for disease treatment.

Give examples of diseases treated with stem cells in animal models.

Diabetes, Parkinson

’s, spinal injury, heart damage, multiple sclerosis, immune deficiency.

What is the Tissue Renewal Principle?

Stem cells divide slowly and self-renew

→ progenitor cells divide rapidly

→ specialised cells perform function.

What ancient discovery showed early tissue repair knowledge?

Indian writings (\sim600 BC) describing skin grafts.

What 18th-century discovery revealed regeneration?

Hydra can regenerate (early regenerative biology).

What 19th-century concept introduced the term

“stem cell

”?

Fertilised egg as origin of all cells.

What early 1900s discoveries were key for stem cell theory?

• Cell culture methods (frog cells in lab) Blood stem cell theory (all blood cells from one ancestor cell) Belief nervous system can

’t regenerate.

What mid-$1900$s discoveries shaped modern stem cell biology?

First cloning (nucleus holds full genome) Pluripotent cells in teratomas Bone marrow stem cells identified First bone marrow transplant.

What were the main 1980s milestones?

Mouse embryonic stem cells isolated Artificial skin made from patient

’s own cells Knockout mice created (missing specific genes).

What were key 1990s discoveries?

Cancer stem cell concept Human embryonic stem cells isolated and cultured.

What was discovered in 2006?

iPSCs

— adult cells reprogrammed into pluripotent stem cells.

What was achieved in 2010 and 2013?

2010: First human stem cell therapy 2013: Stem cells created via therapeutic cloning.

What was proven in 2016?

Reprogrammed skin cells can form new eggs

→ mice grown from skin cells.

What happens during Week 1 of embryonic development?

Fertilisation

→ cleavage

→ compaction

→ blastocyst formation

→ implantation.

What is cleavage?

Rapid mitotic divisions forming smaller cells (blastomeres).

What is compaction?

Cells tightly join via E-Cadherin

→ form a morula.

What is the blastocyst made of?

Inner Cell Mass (forms embryo) Trophoblast (forms placenta) Blastocoel (fluid cavity).

What happens during blastulation?

Embryo reaches the uterus at the blastocyst stage.

What are the 3 main parts of the blastocyst?

Inner Cell Mass, Trophoblast, and Blastocyst Cavity (blastocoel).

What are the two layers formed from the Inner Cell Mass?

Epiblast and Primitive Endoderm (Hypoblast).

What does the epiblast form?

The embryo.

What does the primitive endoderm form?

Extraembryonic tissues (like the yolk sac).

Which genes mark these layers?

Nanog (epiblast) and Gata6 (primitive endoderm).

What does the trophectoderm form?

Placenta and support tissues.

What happens during hatching?

Blastocyst breaks free from the zona pellucida (ZP).

What enzyme helps the blastocyst hatch?

Trypsin-like protease that lys

What are cell/tissue interactions in development?

Cells communicate via embryonic signals. Primary induction example: notochord inducing neural plate formation.

What is the role of cell movement in development?

Cells migrate to specific locations. Short-range and long-range (e.g., neural crest cells). Essential for tissue and organ formation.

What is pattern formation?

Cells develop according to an intrinsic blueprint, controlling spatial arrangement of tissues and organs.

What is folding in embryonic development?

Physical folding shapes the body. Cephalic fold

→ head; caudal fold

→ tail; lateral folds

→ body wall closure.

What is morphogenesis?

Cumulative result of all mechanisms (mitosis, differentiation, folding, etc.) that forms internal and external body structure.

What are maternal genes and their role?

Maternal genes set up the embryo before zygotic genome activation. Products include transcription factors, receptors, regulatory proteins, forming concentration gradients for positional information.

What are zygotic genes and their role?

Genes expressed by the embryo in response to maternal gene signals. Categories: Segmentation genes: divide embryo into segments; define number, size, polarity Selector genes: specify identity/fate of each segment

What happens at fertilization (Day 1)?

Formation of a zygote (single diploid cell), maternal cytoplasm, surrounded by zona pellucida.

What is cleavage (Day 2

–3)?

Rapid mitotic divisions without growth

→ blastomeres. Partition cytoplasm

→ forms blastula with blastocoel.

What is compaction (Day 3)?

Blastomeres tightly adhere via E-CAD. Outer cells

→ trophoblast (placenta); inner cells

→ ICM (embryo proper).