Normal Control of Cell Growth and Differentiation

Question 1

Morphogenesis definition

Answer 1

The biological process that causes an organism to develop its shape. Process controls the spatial distribution of cells during the embryonic development of an organism.

Question 2

three types of tissue

Answer 2

renewing and resting and non dividing

Question 3

Renewing tissue definition

Answer 3

Tissue that continually divides, such as skin with many stem cells

Question 4

Resting tissue

Answer 4

terminally differentiated, cells multiply only to repair damage- hepatocytes will only divide to repair damaged tissue

Question 5

Non dividing tissue

Answer 5

Terminally differentiated, cells will not multiply after birth- neurons, cardiomyocytes

Question 6

What does cell growth require?

Answer 6

Increase in cell mass and volume caused by macromolecular synthesis and relative movement of the cell surface.

Question 7

What controls cell growth and division?

Answer 7

Growth factors that drive proliferation and often act as mitogens

Question 8

How is hyperplasia prevented?

Answer 8

Cell growth balanced by cell loss and cell death

Question 9

How is organ size regulated?

Answer 9

Non autonomous control, release insulin like growth factor signalling controls. Thought that organs have a set point of growth, however in different organs the compartment size Is sensed and correspondingly adjusted.

Lack of a set point suggests that growth is driven by an autonomous program, insensitive to compartment size.

Question 10

Evidence to suggest organ size regulation is autonomous

Answer 10

Transplant many fetal thymuses into developing mice; each grows to the same size.

Question 11

Evidence to suggest organ size regulation is non autonomous

Answer 11

transplant fetal spleens into developing mice; each grows to a different size

Question 12

Apoptosis definition

Answer 12

Death of cells that occurs as a normal and controlled part of an organism’s growth or development. Programmed cell death

Question 13

What biochemical events characterise apoptosis?

Answer 13

Blobbing, cell shrinkage, nuclear fragmentation. chromatin condensation and chromosomal DNA fragmentation

Question 14

What are apoptotic bodies and what happens to them?

Answer 14

Apoptotic cell fragments into vesicles engulfed by phagocytic cells before bioactive contents can spill out and cause damage.

Question 15

Stem cell definition

Answer 15

Undifferentiated cells that are capable of renewal and can divide without limit- produce more specialised cells

Question 16

Two different ways cells are born

Answer 16

exponential, rapid clonal expansion (cell division) or initiating the differentiation of new stem cells

Question 17

Different types of stem cell + definition + example

Answer 17

totipotent- capable of differentiating into all cell types- fertilised egg, morula

pluripotent- capable of giving rise to several different cell types- embryo- give rise to ectoderm, mesoderm and endoderm

multipotent- capable of giving rise to multiple specialised cell types present in a specific tissue or organ

unipotent- has the capacity to differentiated into only one type of cell- skin cell

Question 18

Cell potency definition

Answer 18

The cell’s ability to differentiate into other cell types

Question 19

Committed stem cell definition

Answer 19

can give rise to a smaller subpopulation of cells

Question 20

Explanation of cell renewal in epithelium

Answer 20

Stratum basalum contains proliferating stem cells

Cells move through the different layers of skin, differentiating as they do so, and become sloughed off at the surface

Reach terminal differentiation at the stratum corneum

Question 21

Do stem cells divide often? + why?

Answer 21

No, limit the potential mutations during DNA replication and remains potential for rapid replication at the site of wound repairs

Question 22

What else is present in the skin + function?

Answer 22

Transit Amplifying Cells which are an undifferentiated population in transition which enable tissue regeneration to proceed- bottle neck effect- once the TAC pool forms the regeneration will proceed without return

Question 23

What is the common stem cell in blood?

Answer 23

Multipotent haemopoietic stem cell

Question 24

Examples of blood cells that form

Answer 24

Leucocytes- T cells, B cells, neutrophil, eosinophil, basophil
erythrocytes
platelets, mass cells, osteoclasts, mast cells

Question 25

Evidence for the multi potency of mice

Answer 25

Irradiate the mice, halting blood cell production

Inject bone marrow cells from healthy donor

mouse survives as the injected stem cells colonise its haematopoetic tissue

Question 26

Bone marrow transplant used to treat…

Answer 26

severe aplastic anaemia, leukaemia, non-hodgkin’s lymphoma

Question 27

Induced Pluripotent Stem Cell definition

Answer 27

A type of pluripotent stem cell that can be generated directly from adult cells

Question 28

Explain how cells are reprogrammed into stem cells

Answer 28

Shinya Yamanaka added four reprogramming factors, Oct4, Sox2, Klf4, and c-Myc, into fibroblasts

Delivered by viral vectors, which reverted the genome to its pluripotent state

Question 29

Why are IPS cells important?

Answer 29

Able to generate any cell type, especially important as it can produce new neurons, which normally don’t proliferate- show potential in treating Parkinson’s disease

Question 30

Similarities between differentiated cells

Answer 30

Similar set of organelles, express some common proteins from housekeeping genes

Question 31

Differences between differentiated cells

Answer 31

express cell specific proteins not expressed in undifferentiated cells which lead to specialised functions and structures

Question 32

When does differentiation take place?

Answer 32

During the cell cycle, often before S

Question 33

What produces cells with different functions?

Answer 33

Different genes are expressed- euchromatin whilst others are silenced- heterochromatin, so different proteins are produced . However genome is not altered in sequence

Question 34

Fate definition

Answer 34

Fate of a cell describes what it will become in the course of normal development

Question 35

How is the fate of a particular cell determined?

Answer 35

Label the cell and observe what structures it later becomes apart of.

Question 36

Determination of a cell definition

Answer 36

Involves progressive restrictions in a cell’s potency. The cell ‘chooses’ a particular fate however it still looks the same to its undetermined neighbours. Implies a stable change, the fate of the determined cell does not change.

Question 37

A committed cell definition

Answer 37

Cell is not yet determined, so its fate could be changed

Question 38

What is cellular differentiation controlled by? + explanation

Answer 38

Cellular signals, mainly growth factors. Often the steps are as follows:

1. Ligand produced by a TAC binds to a receptor on an extracellular region of the cell
2. Receptor undergoes a conformational change
3. this changes the shape of the cytoplasmic domain, acquiring enzymatic activity
4. Receptor catalyses reactions that phosphorylate other proteins, activating them causing a phosphorylation cascade
5. Eventually activates a dormant transcription factor thus contributing to differentiation

Also controlled by epigenetics

Question 39

How is determination and commitment shown in the trilaminar disc?

Answer 39

Ectoderm upon mesoderm upon endoderm.

If mesoderm is removed, the ectoderm in contact with endoderm will become mesoderm, suggesting that the endoderm is determined, whereas the ectoderm is not and ligands are released from the endoderm