Lecture 4 - Cell Differentiation and Neural Induction IV

Question 1

embryonic self regulation study

Answer 1

killed one cell in 2-frog embryo, blastula formed half an embryo

Question 2

embryonic self regulation study (conclusions)

Answer 2

frogs develop in mosaic form (mitotic lineage); possible dead cells affected development on neighboring cells

Question 3

self regulation study 2

Answer 3

separate 4 cells in early hydra and all 4 produced a full-bodied hydra > every cell is capable of producing any type of cell

Question 4

self regulation

Answer 4

the ability to change fate in order to compensate for the loss of other cells (limits as embryo grows)

Question 5

totipotency

Answer 5

the ability of embryonic cell to take any fate

Question 6

embryonic stem cells

Answer 6

found in embryos that display totipotency

Question 7

conditional specification of cell fate

Answer 7

cell fate depends on environmental conditions (guided by cell-cell interactions)

Question 8

the European plan

Answer 8

emphasizes ancestry to determine cell fate

Question 9

the American plan

Answer 9

emphasizes effect of neighboring cells on cell fate

Question 10

transgene

Answer 10

a gene that has been artificially introduced into a model organism

Question 11

chimera

Answer 11

an organism made up of cells displaying more than one genotype, formed from the combo of cells from two separate zygote

Question 12

transgenic

Answer 12

an organism where foreign DNA has been inserted

Question 13

Morgan

Answer 13

dead cells affected sister cells in frog experiment (removed 1/2 blastomere)

Question 14

Spemann

Answer 14

as long as the other cell has at least 1 nucleus, 1 cell give rise to whole organism (salamander)

Question 15

Weismann

Answer 15

removed cells, didn’t affect body plan - cells replaced

Question 16

formation of the optic cups

Answer 16

neural tube extends optic cups out to epithelium

Question 17

optic cups

Answer 17

give rise to retina, overlying epithelium produce lens and cornea

Question 18

optic cup study

Answer 18

removed 1 optic cup, no lens induced; moved optic cup to random epithelium, lens induced but on head (cells in trunk not competent)

Question 19

dorsal lip

Answer 19

the embryonic region that can induce/direct development of a second NS and second individual embryo

Question 20

dorsal lip study

Answer 20

transplant dorsal lip of blastopore from pigmented newt to unpigmented newt > formed some new structures and new individual (unpigmented conjoined twins)d

Question 21

dorsal lip study conclusion

Answer 21

cells in the dorsal lip are organizer > trigger cascade of inductive processes

Question 22

isolating noggin test 1

Answer 22

exposed xenopus embryos to LiCl then extract mRNA from dorsal lip, inject into UV exposed embryos

Question 23

noggin results

Answer 23

injecting mRNA into UV exposed embryos rescue animals (expose normal heads)

Question 24

noggin test 2

Answer 24

Extract RNA from dorsal lip treated with LiCl to make cDNA library, inject mRNA from library to UV treated embryo

Question 25

noggin result 2

Answer 25

noggin isolated that rescued UV treated embryos, with too much they get giant head like with LiCl

Question 26

chordin

Answer 26

encodes for protein chordin - organizer effect on ectoderm, shifting to neural fate

Question 27

follistatin

Answer 27

same as chordin but encodes for follistatin gene

Question 28

BMP

Answer 28

growth factors that act to encourage ectodermal cells to take on epidermal fate

Question 29

TGFbeta receptors

Answer 29

bind BMPs

Question 30

expression of chordin and follistatin

Answer 30

in dorsal lip of blastopore, protein product could also induce ectodermal cells to differentiate into cells of NS

Question 31

antagonists of BMP

Answer 31

noggin, chordin, follistatin

Question 32

BMP4

Answer 32

secreted by ectodermal cells which also secrete receptor; inhibits neural fate

Question 33

mesoderm and BMP4

Answer 33

releases organizers and disrupts BMP4 signaling by blocking receptors; induces overlying ectoderm to become NS

Question 34

formation of neural plate

Answer 34

induced by organizers and BMP (mesoderm secretion)

Question 35

notochord formation

Answer 35

mesodermal cells secreting organizer protein compress laterally until they form rodlike structure on midline

Question 36

distribution of signals

Answer 36

ectodermal layer have few signals (why they take epidermal fate), neural tube gets highest does & strongest blockage of BMP (NS), random in between cells have moderate blockage which is why they’re neural crest (PNS)