M1. models of development

Question 1

two main theories of embryo development

Answer 1

mosaic vs. regulative

Question 2

mosaic development (history)

Answer 2

~german embryologist wilhelm roux (1880s)
~one cell of the two cell frog embryo was destroyed
~remaining cell developed into a well formed half embryo

Question 3

mosaic development

Answer 3

asymmetric cell division leads to unequal distribution of cell fate determinants

Question 4

mosaic development can require cytoplasmic determinants

Answer 4

-proteins and / or mRNAs located in the cytoplasm that are distributed unequally during cell division making daughter cells different from one another

Question 5

mosaic development can require cell polarity

Answer 5

-unequal distribution of cytoplasmic / cell membrane components
~cells have their character and fate determined at each cell division
~ often involves relocation of molecules to one side of the cell using the cell’s cytoskeleton

Question 6

mosaic development cytoskeleton

Answer 6

microtubules and microfilaments are essential structures of the cytoskeleton
-the fibrous network of structural proteins that maintain and regulate mechanical functions within the cell

Question 7

microtubules

Answer 7

~polymers of tubulin subunits; (+) and (-) ends
~emanate from centrioles during mitosis ~motor proteins move cargo (red) with dynein (-end motor) and kinesin (+ end motor)

Question 8

microfilaments

Answer 8

~polymers of actin subunits, part of fibrous network under cell membrane
~associated with cell membrane movement (filopodia (b)) , (lamelopodia (a)), cell adhesion (focal adhesions (c)), stress fibres, contraction (actinomyosin)

Question 9

regulative development (history)

Answer 9

german embryologist Hans Driesch
~destroyed one cell of the two cell sea urchin embryo
~a complete, but smaller larvae formed

Question 10

regulative development

Answer 10

~depends upon interaction between cells of the embryo

~tissues can restore normal development even if parts of the embryo are removed and/or rearranged

Question 11

Induction

Answer 11

• a type of regulatory development

- one tissue directs the development of another tissue

Question 12

the spemann-mangold organizer

Answer 12

regulatory development

-can induce the formation of a second embryo

Question 13

hans spemann

Answer 13

received the nobel prize for physiology or medicine in 1935-first award given for embryological research

Question 14

the spemann-mangold organizer: hans spemann hilde mangold (1924) steps

Answer 14

1) used newt embryos of two different species with a differing pigment colour
2) grafted of the blastopore lip of one newt onto another 3) the blastopore is the opening formed in early gastrulation through which cell migrate inside
4) the graphed blastopore lip (i.e Spemann-Mangold organizer) can indcue the formation of a ectopic axis (a complete embryonic body)
5) the graphed donor tissue is able to induce host tissue to form parts of new embryo, this induction changes the normal developmental fate of the host tissue

Question 15

french flag model (FFM)

Answer 15

patterning can involve the interpretation of positional info (lewis wolpert 1969)

Question 16

positional info

Answer 16

directs pattern formation by giving positional values to cells

Question 17

FFM colours?

Answer 17

1) the blue, white and red stripes refers to the fate (i.e. the type of cell) of cells within a field of cells

Question 18

FFM morphogen

Answer 18

2) morphogen —> any substance that has a variable concentration (i.e. can form a gradient) and is involved in pattern formation

Question 19

FFM positional info

Answer 19

3) positional information —> interpreted as depth of gradient of a morphogen - requires field polarity

Question 20

FFM positional value

Answer 20

4) positional value —> threshold concentrations instruct cell identity - thresholds relate to a boundary

Question 21

FFM: need for ____ maintenance

Answer 21

gradient (a morphogen source and sink)

Question 22

FFM threshold concentrations

Answer 22

2) threshold concentrations —> different fates are specified by a range of a morphogen concentration

Question 23

FFM separation of value and interpretation

Answer 23

3) separation of value and interpretation — allows for same gradient to generate different fates

Question 24

FFM mechanism for regulative development

Answer 24

4) mechanism for regulative development — absolute size of system can change but patterning maintained

Question 25

FFM regeneration of pattern

Answer 25

5) regeneration of pattern — gradient can reform — gaps can signal for reformation