intro to developmental biology

features of a good animal model

• reproduce quickly

• short life cycle

• share anatomical, physiological or genetic pathways to humans

• easy to maintain in a lab

drosophila

• short life cycle

• easy to maintain in a lab

• rapid life cycle

• fully sequenced genome

• easily mutated

amniotes

• phylogenetically closer to humans

• mice have prolific breeding, vast resource of defined genetic strains, sophisticated genetic mutation techniques

• chickens develop externally

anamniotes

• external development so observable and accessible

• large number of eggs

• rapid development

• short life cycle

• transparent

• easy to mutate

• sequenced genome

what are pgcs

• primordial germ cells

• stem cells which are precursors to gametes

• migrate to the genital ridges

• then they proliferate

• then meiosis

what is cleavage

• zygote undergoes multiple rapid rounds of cell division becoming smaller

• these cells are called blastomeres

• each cell touches zona pellucida

• morula at 16 stage

morula

• inner core of cells

• superficial layer of cells

• inner core cells become the embryo

• superificial layer becomes extra embryonic membrane

blastocyst

• cells on the outside pump fluid into embryo to form blastocyst cavity

• outer cell mass and inner cell mass

• (trophoblast and embryoblast)

• blastula

hatching

• blastocyst breaks free from zona pellucida

• starts to grow

implantation

• blastocyst attaches to uterine lining

• trophoblast adheres firmly to endometrium then penetrates

• trophoblast differentiates into cytotrophoblasts (embed embryo) and syncytiotrophoblasts (fuses with endometrium and secretes enzymes that digest uterine lining)

• embryoblast divides into epiblast and hypoblast forming a 2 layered structure called the bilaminar disk

• amniotic cavity forms within epiblast

• syntiotrophoblast becomes continuous with the uterus so maternal blood vessles invade lacunae there