Lecture 11 - Mechanisms of Development

Question 1

Are there similar patterns of development amongst species?

Answer 1

YES! No matter what species they are all very similar e.g. eyes, limb, mouth being developed. Happens in all species.

Question 2

What is gastrulation?

Answer 2

A critical point in development at which the pluripotent cells suddenly lose pluripotency and turn into the 3 multipotent germ layers (ecto, meso & endoderm). From here these three layers differentiate into more specific cells e.g. muscle, blood etc.

Question 3

During gastrulation, cells go from ___potent to ___potent to ___potent.

Answer 3

Pluri –> multi –> uni

Question 4

What are the 4 essential cellular processes for multicellular organisms?

Answer 4

1. Cell proliferation
2. Cell specialisation
3. Cell interaction
4. Cell movement

Question 5

What are two types of protein classes that exist in great number across all multicellular organisms? E.g. a mouse is lacking a specific protein so take it out of fruit fly and put into mouse and mouse can function normally

Answer 5

1. Transmembrane molecules e.g. for cell adhesion or signalling
2. Gene regulatory (DNA binding) proteins

Question 6

What are 3 ways cell identity can be maintained?

Answer 6

CELL IDENTITY through:

1. Positive feedback loop
2. DNA methylation
3. Chromatin remodelling

Question 7

What is another way cell identity can be maintained? What is 2 examples of master genes?

Answer 7

Through MASTER GENES (e.g. MyoD & ey) & GENE CIRCUITRY
E.g. put eye gene where leg gene is in a fly and an eye will grow on the leg
Master genes set up self-reinforcing circuits that cause other cells to change their identities

Question 8

What is the difference between symmetric & asymmetric division?

Answer 8

Symmetric: sister cells become deifferent as a result of signals acting on them after birth
Asymmetric: the sister cells are born different

Question 9

How do we create a morphogen gradient? Through the additon of ___ and ___.

Answer 9

Inducers and inhibitors.

Question 10

1. Morphogens + Receptors =

2. Morphogens + Inhibitors =

Answer 10

1. Cellular Response. Each type of morphogen has its own different receptor.
2. No Response

Question 11

What are two examples of morphogens in sonic hedgehog gradients?

Answer 11

1. Chick limb development - cut it out and insert it somewhere else and limb will grow
2. Lung branching morphogenesis

Question 12

What is one molecule crucial in cell-cell adhesion?

Answer 12

Cadherins

Question 13

What is ‘sorting out’ in relation to cadherins? What drives the sorting out?

Answer 13

• e.g. E and N cadherins produced all mixed together. The cells will ‘sort’ themselvesso that the N cadherins are on the outside and the E cadherins are on the inside.
• Ca2+ needs to be added for sorting out to occur

Question 14

What is one molecule crucial in cell-ECM adhesion?

Answer 14

Integrins & ECM proteins

Question 15

What is a morphogen?

Answer 15

An inductive signal