Fie Thijs Experiments Developmental Biology 2025-2026
EXPERIMENTS
CHAPTER 1 – OVERVIEW OF VERTEBRATE DEVELOPMENT
1.1 – THE FROG DEVELOPMENT
• Induced egg laying -> intradermal injection of hCG hormone
o Inject urine of woman -> ovulation triggered = woman is pregnant
• Change temperature = change speed of development
• Change genotype of mother = genotype of embryo changes as well
• Visualization of mesoderm movement
o Whole-mount in situ hybridization
o Labelling mesodermal cells with fluorescent dye (e.g. mRNA-GFP)
▪ Follow cells from mid-gastrula until late-gastrula stage
▪ See medio-lateral intercalation behavior
1.2 – THE MAMMALIAN DEVELOPMENT
• Use mice for
o Genetic studies (e.g. changing coat colors)
o Study radioactivity of atomic bombs
o Inbreed
▪ Cross brother and sister -> after 10 generations = clones
o Outbreed
▪ No clones
o Mutant mice
▪ Via gene targeting or gene knock-outs
▪ Embryonic blastocyst stem cells -> modified
▪ Inserted back and let it develop
• Genetic manipulation by using inner cell mass embryonic stem cells
3BA Biology 1
, Fie Thijs Experiments Developmental Biology 2025-2026
CHAPTER 2 – EXPERIMENTAL EMBRYOLOGY
2.1 – REGULATIVE VERSUS MOSAIC DEVELOPMENT
• August weismann refutes Lamarck’s theory of inheritance of acquired traits
o Cuts tail of mice for 22 generations -> no offspring with short tail
o Theory is false
• Wilhelm Roux – tests germ plasm theory by Weismann
o 2-cell stage of amphibian embryo
o Kill 1 blastomere with hot needle – leave it attached to living blastomere
o ° half an embryo -> mosaic development
• Hans Driesch – tests germ plasm theory
o 2-cell stage sea urchin – separates blastomeres
o Each develops into normal, but smaller, larvae -> regulative development
• Hans Driesch – tests nuclear located determinants
o 8-cell stage sea urchin -> pressure with glass plate
o Cells were next to each other -> now below each other
o Normal embryo = nuclei rearranged so determinants are not in nucleus!
• Sven Horstadius – tackles controversy between 2 theories
o 8-cell stage sea urchin
o Separates horizontally = animal vs vegetal pole (Mosaic)
▪ Vegetal = mildly abnormal
▪ Animal = blob
o Separates along animal-vegetal pole = vertical (Regulative)
▪ 2 normal larvae
o OR vegetal blastomeres = special characteristic for normal development
• Sven Horstadius – localize characteristic in vegetal blastomeres
o Unfertilized egg cut in 2
▪ Animal vs vegetal – after fertilization = 1 normal & 1 abnormal larvae
▪ Along animal-vegetal axis – after fertilization = 2 normal larvae
o Vegetal cytoplasmic determinant present
o Determinant is cytoplasmic – along a-v axis = only 1 side has nucleus
o Determinant is vegetal = only animal pole results in abnormal larvae
• Hans Spemann – totipotency until 16 cell-stage
o Ligation – cytoplasmic bridge but nucleus only on 1 side
o Develop until 16-cell stage -> open ligature -> 1 nucleus vs 15 nuclei
o Develop = 2 normal embryo -> totipotency proved
o Also tested germ plasm theory with plane of separation = same results
3BA Biology 2
EXPERIMENTS
CHAPTER 1 – OVERVIEW OF VERTEBRATE DEVELOPMENT
1.1 – THE FROG DEVELOPMENT
• Induced egg laying -> intradermal injection of hCG hormone
o Inject urine of woman -> ovulation triggered = woman is pregnant
• Change temperature = change speed of development
• Change genotype of mother = genotype of embryo changes as well
• Visualization of mesoderm movement
o Whole-mount in situ hybridization
o Labelling mesodermal cells with fluorescent dye (e.g. mRNA-GFP)
▪ Follow cells from mid-gastrula until late-gastrula stage
▪ See medio-lateral intercalation behavior
1.2 – THE MAMMALIAN DEVELOPMENT
• Use mice for
o Genetic studies (e.g. changing coat colors)
o Study radioactivity of atomic bombs
o Inbreed
▪ Cross brother and sister -> after 10 generations = clones
o Outbreed
▪ No clones
o Mutant mice
▪ Via gene targeting or gene knock-outs
▪ Embryonic blastocyst stem cells -> modified
▪ Inserted back and let it develop
• Genetic manipulation by using inner cell mass embryonic stem cells
3BA Biology 1
, Fie Thijs Experiments Developmental Biology 2025-2026
CHAPTER 2 – EXPERIMENTAL EMBRYOLOGY
2.1 – REGULATIVE VERSUS MOSAIC DEVELOPMENT
• August weismann refutes Lamarck’s theory of inheritance of acquired traits
o Cuts tail of mice for 22 generations -> no offspring with short tail
o Theory is false
• Wilhelm Roux – tests germ plasm theory by Weismann
o 2-cell stage of amphibian embryo
o Kill 1 blastomere with hot needle – leave it attached to living blastomere
o ° half an embryo -> mosaic development
• Hans Driesch – tests germ plasm theory
o 2-cell stage sea urchin – separates blastomeres
o Each develops into normal, but smaller, larvae -> regulative development
• Hans Driesch – tests nuclear located determinants
o 8-cell stage sea urchin -> pressure with glass plate
o Cells were next to each other -> now below each other
o Normal embryo = nuclei rearranged so determinants are not in nucleus!
• Sven Horstadius – tackles controversy between 2 theories
o 8-cell stage sea urchin
o Separates horizontally = animal vs vegetal pole (Mosaic)
▪ Vegetal = mildly abnormal
▪ Animal = blob
o Separates along animal-vegetal pole = vertical (Regulative)
▪ 2 normal larvae
o OR vegetal blastomeres = special characteristic for normal development
• Sven Horstadius – localize characteristic in vegetal blastomeres
o Unfertilized egg cut in 2
▪ Animal vs vegetal – after fertilization = 1 normal & 1 abnormal larvae
▪ Along animal-vegetal axis – after fertilization = 2 normal larvae
o Vegetal cytoplasmic determinant present
o Determinant is cytoplasmic – along a-v axis = only 1 side has nucleus
o Determinant is vegetal = only animal pole results in abnormal larvae
• Hans Spemann – totipotency until 16 cell-stage
o Ligation – cytoplasmic bridge but nucleus only on 1 side
o Develop until 16-cell stage -> open ligature -> 1 nucleus vs 15 nuclei
o Develop = 2 normal embryo -> totipotency proved
o Also tested germ plasm theory with plane of separation = same results
3BA Biology 2
