MODULE 7: Developmental Biology

Question 1

Hemorrhagic Stroke

Answer 1

blood leaks into brain tissue

Question 2

Ischemic Stroke

Answer 2

clot stops blood supply to area of brain

Question 3

Broca’s Aphasia

Answer 3

inability to put words together to form complete sentences

Question 4

Hemiparesis

Answer 4

weakness of entire half of body sue to damaged motor cortex from a stroke

Question 5

Types of Stem Cells

Answer 5

Totipotent:

• unlimited capability
• ability to form pre and post embryonic membranes and tissues

Pluripotent:
- give rise to most tissues

Multipotent:
- give rise to cells with specific function

Question 6

Embryonic Development

Answer 6

Day 0: Pronuclear phase
Day 1: 2-cell
Day 2: 4-cell
Day 3: 8-cell
Day 5: blastocyst
Day 6: blastocyst enters uterus and sheds "shell", embeds in uterine wall

Question 7

Embryonic Stem Cells (ESCs)

Answer 7

imortal cell that propagates indefinitely

has potential to differentiate into a cell of any germ layer

pluripotent

Question 8

Haematopoietic Stem Cell Transplant

Answer 8

• transplant bone marrow

- donor bone marrow cells repopulate recipient bone marrow

Question 9

Vision - Limbic Stem Cell Transplant

Answer 9

sclera: whites
conjunctiva: clear, thin membrane that covers sclera
cornea: transparent layer over eye
limbus: barrier between iris and sclera, adult stem cells

an outer epithelium and inner endothelium that sandwiches a fibrous matric containing keratocytes (fibroblasts unique to cornea)

dispersed corneal cells cultures for 2 weeks on special substrates

stem cells become artificial cornea

transplantation involves microsurgery - artificial cornea sewn onto eye

Question 10

Induced Pluripotent Stem Cells / Problems

Answer 10

• 4 genes sufficient to make embryonic stem cell remain as pluripotent stem cell
• every cell of body has these 4 genes but different expression
• inserts 4 genes into inner cell mass (already contains the 4 genes)
• make cells express genes
• fibroblast sees product of these genes and is converted back to ESC
• occurs over 3 weeks
• these cells replicate until identical to ESCs which can then produce any cell in body
• can also be derived from some somatic cells

Problems:

1) low efficiency
2) choice of somatic cell (DNA mutations?)
3) do transgenes cause mutations?
4) does reprogramming cause mutations

Question 11

Transdifferentiation

Answer 11

iPSC:
differentiated cell —-> iPSC —> another differentiated cell

Transdifferentiation:
differentiated cell —-> another differentiated cell

• eliminates possible mutations
• 4 different genes make up specific cell e.g. blood stem cells
• transferred these genes into endothelial cells to make blood stem cells

Question 12

Skin - Generating Stem Cells

Answer 12

• one neonatal foreskin contains enough genetic material to grow 250,000 square feet of skin
• during manufactoring process, human fibroblasts are seeded
• human fibroblasts proliferate to fill the interstices of scaffold
• human fibroblast secrete dermal collage, matrix proteins, growth factors and cytokines to create 3D human dermal substitute

Question 13

Generating Stem Cells From Blastocysts

Answer 13

• collect inner cell mass and palce in culture
• purify embryonic stem cells
• ESCs make any cell in body
• kills embryo

Question 14

Cloning - Somatic Cell Nuclear Transfer

Answer 14

• take on oocyte (unfertilised egg) by giving hormones to female –> super ovulation –> collect eggs
• suck out nucleus with micropipette to have empty cell
• remove nucleus from blastocyst and inject into empty oocyte to give artificially fertilised oocyte (contains nucleus with two chromosomes)
• oocyte divides to form embryo —> blastocyst
• collect inner cell mass from this blastocyst
• ESCs form any cell in body