Embryology
EMBRYOLOGY............................................................................................................................................... 1
WHAT IS EMBRYONIC DEVELOPMENT?.........................................................................................................................2
WHERE DOES EMBRYOLOGY START?............................................................................................................................2
GAMETOGENESIS.......................................................................................................................................... 2
MITOSIS VS MEIOSIS.................................................................................................................................................2
Meiosis I..........................................................................................................................................................2
SPERMATOGENESIS:..................................................................................................................................................3
Spermiogenesis:..............................................................................................................................................3
OOGENESIS:............................................................................................................................................................3
Sperm transport..............................................................................................................................................4
FERTILIZATION:.........................................................................................................................................................4
Sperm capacitation.........................................................................................................................................4
Attachment to\penetration of corona radiata & zona pellucida (ZP)............................................................4
Attachment to and penetration of plasma membrane of oocyte...................................................................4
Penetration results in a wave of calcium spreading from site of sperm entry resulting in:...........................4
CLEAVAGE...............................................................................................................................................................5
BLASTOCYST FORMATION...........................................................................................................................................5
CELL “POTENCY”......................................................................................................................................................5
Monozygotic Twins.........................................................................................................................................6
Pre-implantation genetic diagnosis................................................................................................................6
HATCHING & IMPLANTATION......................................................................................................................................6
BILAMINAR EMBRYO.................................................................................................................................................6
GASTRULATION........................................................................................................................................................8
Epiboly:............................................................................................................................................................8
Ectoderm:........................................................................................................................................................8
Mesoderm:......................................................................................................................................................8
Endoderm:.......................................................................................................................................................8
NEURAL INDUCTION:.................................................................................................................................................8
NEURULATION:........................................................................................................................................................9
What is the Neural Crest?...............................................................................................................................9
EMBRYOLOGY............................................................................................................................................. 10
TRACING THE NEURAL CREST:...................................................................................................................................10
Radioisotopic labelling:.................................................................................................................................10
Quail-chick chimeras.....................................................................................................................................10
Transgenic Green Fluorescent Protein (GFP) chickens..................................................................................10
FOLDING OF THE EMBRYO........................................................................................................................................11
LIMB DEVELOPMENT...............................................................................................................................................11
Limb bud initiation:.......................................................................................................................................11
Molecular mechanisms:................................................................................................................................11
Limb bud outgrowth.....................................................................................................................................11
1
, Embryology
- Process of development from a single fertilized egg to a fully formed organism.
- Carnegie stages, 23 stages of human embryonic development.
What is embryonic development?
- involved many important cellular processes:
o Cell division
o Cell migration
o Cell shape change
o Cell differentiation (specialization through differing gene expression)
o Cell death
- Extensively studied in human as well as many other model organisms, which give
insight into genetic processes.
Where does embryology start?
- Fertilization: merging of 2 gametes, the egg and sperm, to form an embryo.
Gametogenesis
- Females: in Ovaries. Males: in testes
- Gamete form from primordial germ cells
- Main steps in the process:
o Increase in the number of germ cells by mitosis
o Decrease in chromosome number in the germ cells by meiosis.
o Structural and functional changes leading to the maturation of egg and
sperm.
Mitosis vs Meiosis
- Both start with a cell with 23 pairs of chromosomes (diploid, 2n)
- Chromosomes are replicated during interphase forming 2 sister chromatids joined by
a centromere
- Mitosis splits the sister chromatids into 2 diploid daughter cells (2n)
- Meiosis produces 4 daughter cells that are haploid (1n) through 2 successive cell
divisions: Meiosis I and Meiosis II.
Meiosis I
Prolonged Prophase I:
- Homologous chromosomes form tetrads by synapsis.
o Called crossing over: exchange of DNA between maternal and paternal
chromosomes creates genetic variation in resulting gametes.
o Chiasmata = point where chromosomes are joined together.
Metaphase I:
- Independent Assortment
o Way that chromosomes line up is random
o Genetic variation in resulting gametes.
2
EMBRYOLOGY............................................................................................................................................... 1
WHAT IS EMBRYONIC DEVELOPMENT?.........................................................................................................................2
WHERE DOES EMBRYOLOGY START?............................................................................................................................2
GAMETOGENESIS.......................................................................................................................................... 2
MITOSIS VS MEIOSIS.................................................................................................................................................2
Meiosis I..........................................................................................................................................................2
SPERMATOGENESIS:..................................................................................................................................................3
Spermiogenesis:..............................................................................................................................................3
OOGENESIS:............................................................................................................................................................3
Sperm transport..............................................................................................................................................4
FERTILIZATION:.........................................................................................................................................................4
Sperm capacitation.........................................................................................................................................4
Attachment to\penetration of corona radiata & zona pellucida (ZP)............................................................4
Attachment to and penetration of plasma membrane of oocyte...................................................................4
Penetration results in a wave of calcium spreading from site of sperm entry resulting in:...........................4
CLEAVAGE...............................................................................................................................................................5
BLASTOCYST FORMATION...........................................................................................................................................5
CELL “POTENCY”......................................................................................................................................................5
Monozygotic Twins.........................................................................................................................................6
Pre-implantation genetic diagnosis................................................................................................................6
HATCHING & IMPLANTATION......................................................................................................................................6
BILAMINAR EMBRYO.................................................................................................................................................6
GASTRULATION........................................................................................................................................................8
Epiboly:............................................................................................................................................................8
Ectoderm:........................................................................................................................................................8
Mesoderm:......................................................................................................................................................8
Endoderm:.......................................................................................................................................................8
NEURAL INDUCTION:.................................................................................................................................................8
NEURULATION:........................................................................................................................................................9
What is the Neural Crest?...............................................................................................................................9
EMBRYOLOGY............................................................................................................................................. 10
TRACING THE NEURAL CREST:...................................................................................................................................10
Radioisotopic labelling:.................................................................................................................................10
Quail-chick chimeras.....................................................................................................................................10
Transgenic Green Fluorescent Protein (GFP) chickens..................................................................................10
FOLDING OF THE EMBRYO........................................................................................................................................11
LIMB DEVELOPMENT...............................................................................................................................................11
Limb bud initiation:.......................................................................................................................................11
Molecular mechanisms:................................................................................................................................11
Limb bud outgrowth.....................................................................................................................................11
1
, Embryology
- Process of development from a single fertilized egg to a fully formed organism.
- Carnegie stages, 23 stages of human embryonic development.
What is embryonic development?
- involved many important cellular processes:
o Cell division
o Cell migration
o Cell shape change
o Cell differentiation (specialization through differing gene expression)
o Cell death
- Extensively studied in human as well as many other model organisms, which give
insight into genetic processes.
Where does embryology start?
- Fertilization: merging of 2 gametes, the egg and sperm, to form an embryo.
Gametogenesis
- Females: in Ovaries. Males: in testes
- Gamete form from primordial germ cells
- Main steps in the process:
o Increase in the number of germ cells by mitosis
o Decrease in chromosome number in the germ cells by meiosis.
o Structural and functional changes leading to the maturation of egg and
sperm.
Mitosis vs Meiosis
- Both start with a cell with 23 pairs of chromosomes (diploid, 2n)
- Chromosomes are replicated during interphase forming 2 sister chromatids joined by
a centromere
- Mitosis splits the sister chromatids into 2 diploid daughter cells (2n)
- Meiosis produces 4 daughter cells that are haploid (1n) through 2 successive cell
divisions: Meiosis I and Meiosis II.
Meiosis I
Prolonged Prophase I:
- Homologous chromosomes form tetrads by synapsis.
o Called crossing over: exchange of DNA between maternal and paternal
chromosomes creates genetic variation in resulting gametes.
o Chiasmata = point where chromosomes are joined together.
Metaphase I:
- Independent Assortment
o Way that chromosomes line up is random
o Genetic variation in resulting gametes.
2
