lec 2- how a single cell gives rise to an organism Flashcards
what are the two ways a single cell, give rise to a complex, multicellular organism?
- multiple rounds of cellular division
- cells take on different identities and develop into specific organs, limbs, and other parts of the organism, must occur in correct time and space
what processes overlap in time and space during embryogenesis?
cleavage, pattern formation, morphogenesis, cell differentiation, and growth
what is cleavage?
after the cell is fertilized, multiple rounds of cell division occur which divide the zygote into smaller cells
what is pattern formation?
the organization of cells so a correctly organized embryo can form, overall body plan is laid down
what are the main body axes of an embryo with a head and a tail?
anterior = head
posterior = tail
Dorsal = back
ventral = front
right
left
what are the germ layers of pattern formation of vertebrates and what do they give rise too?
endoderm = guts, liver, lungs
mesoderm = skeleton, muscle, kidney, heart, blood
ectoderm = epidermis of skin, nervous system
what are the germ layers of insects and what do they do?
endoderm = gut
mesoderm = muscle, heart, blood
ectoderm = cuticle, nervous system
what are the axis in pattern formation of plants?
apical-basal axis = shoot to root
radial axis = centre of stem outwards
when do both of the axes in a plant form?
during embryogenesis
what is morphogenesis?
development of shape or morphology
what happens during morphogenesis in animals?
gastrulation occurs, endoderm and mesoderm move inside, creating the gut mouth and anus
what happens during morphogenesis in plants?
morphogenesis occurs throughout a plants life and forms leaves, stems, flowers, and roots
what is the difference between animal and plant morphogenesis?
animal morphogenesis only occurs during embryogenesis and cell move, while in plants it occurs throughout their lifee and no cell movement occurs, rather they expand their cells
does morphogenesis allow a plant to change its form in response to the environment?
yes
what is cell differentiation?
the process by which cells become different from one another
are pattern formation, morphogenesis and cell differentiation closely related processes?
yes
how long does it take for an embryo to grow in humans?
form established in 8 weeks, and growth occurs later
what are the 3 steps for a cell to become different?
- specification: cell aquire the ability to develop into a certain cell type, can change if different signals received, specified if develop without signals
- determination: stable change in the identity of the cell, it can’t turn into any other cell type
- differentiation: cell takes on its final identity
what happens inside cells as they develop from an undifferentiated state into specific cell types?
changes in gene expression occur
how do scientists figure out the specific fates of embryonic cells?
fate mapping experiments
what is the cell labelling experiment?
when the cell is labelled early and scientists look at later stages to see what happened to the marked cells
how do scientists know if a cell is specified?
by the isolation experiment
what is the isolation experiment?
scientists remove the cell and culture them in an area devoid of signals, if the cell still takes on its original fate, it is specified
how do scientists tell if a cell is determined?
by the transplantation experiment
what is the transplantation experiment?
scientists take a cell from one side of the embryo and put it on the other side, if it keeps its original fate, it was determined
