Pt. 2 & Chapter 4 Flashcards
what are the four steps of cell differentiation?
- competence
- induction
- commitment (specification, determination)
- differentiation
what is specification?
recieves signal, induced in neutral environment (no signals from neighbors)
what are the three types of specification? describe them
autonomous
- dependent on cytoplasmic factors
- knows what to do when separated
conditional / regulative
- dependent on morphogens & induction
- dependent on neighbors if it has them
syncytial
- single cells w/ many nuclei
- act like morphogens & make gradients
what is determination?
altered TFs (maintenance processes)
- starting to do the signal
- remain induced in conflicting environment
what are morphogens?
threshold gradient (red & blue, in-class demo)
- each level of morphogen determines a specific response
EX: bicoid & nanos
what is in each section of sperm? (head, midpiece, tail)
head
- acrosomal vesicle
- cell MB
- nucleus
midpiece
- centriole
- mitochondira
tail
- flagellum
what does the acrosomal vesicle do?
bag of enzymes that degrade oocyte jelly coat
what is a cumulus?
contains support cells that become corpus lutem
- in mammals
why are sea urchins good model organisms?
- complete meiosis before fertilization
- external fertilization (eggs laid)
- transparent egg & embryo
- gametes huge in #
- easy to see fertilization in lab conditions
why NOT sea urchins as model organisms?
cannot follow for generations, don’t survive
what are the three problems posed with external fertilization? how are the solved?
diluted in entire ocean -> sperm attractant
fertilize wrong species -> bindin binding vitelline en.
multiple fertilization -> fast & slow blocks
what is the process of sea urchin external fertilization?
- egg releases sperm attractant
- sperm contacts jelly layer
- actin extends & pushes acrosome
- acrosome bursts & releases digestive enzymes
- digestion of jelly coat exposes bindin protein
- bindin binds vitelline en. (species-species recognition)
- fusion of acrosomal MB & egg creates a tunnel
- fast block -> opens ion channels (Na+ IN, Cl- OUT)
- slow block -> cortical granules burst & release enzymes
what are the four enzymes released by the cortical granules? functions?
proteases -> cut vitelline ties
polysaccharides
peroxidases
hyalin -> makes fertilization en. to eject sperm
what are the early responses (seconds) of sea urchin fertilization?
- sperm-egg binding
- fast block
- sperm-egg MB fuse
- Ca2+ exocytosis of cortical granules
what are the 1min late responses of sea urchin fertilization?
energy & pH
- activation of kinases & energy (NADPH, etc.)
- sperm entry
- acid efflux (increase pH, more basic)
what are the 10 min late responses of sea urchin fertilization?
migration & proteins
- DNA decondenses
- migration of gametes
- activation of AA synthesis
what are the 20 min late responses of sea urchin fertilization?
cell cycle
- DNA synthesis
- mitosis
- cleavage
what is early cleavage? what controls this?
M -> S phase (no cytokinesis)
- Cdc2 / cyclinB (on/off switch)
- allows DNA to double
- made during S-phase, active during M-phase, degraded after M-phase
- activates MPF (mitosis promoting factor) that drives shift from M -> S
- does this 10x
what is late cleavage?
full cell cycle
- cells now start to change & differentiate
what is holoblastic cleavage? what are the three types?
entire cell divides, including yolk
- radial
- rotational
- displaced radial
describe the differences between the three types of holoblastic cleavage
radial: rotate 90 around center
rotational: cut from side at an angle, uneven
displaced radial: yolk parts divide slower
what is meroblastic cleavage? what are the two types?
only embryo divides, not yolk
- discoidal
- centrolectihal (syncitium)
describe the differences between the two types of meroblastic cleavage?
discoidal: cells divide ontop of yolk
centrolectihal: superficial, many nuclei around outer MB
what is invagination?
creates a pore
what is involution?
cells move inward to create a new lining of cells
what is ingression?
cells leave the layer individually & migrate inward
what is delamination?
makes layer thicker, cells remain same type & property
what is epiboly?
outer layers thin & stretch to cover entire embryo
