MCDB 120 Section #6
November 7, 2007
TA: Michael Fiedler
Give 5 examples of a “model organism”?
What is the advantage of each and why
are they utilized?
(fly) – cheap, grow fast, genetics are easily manipulated,
good for general embryogenesis
(frogs) – generate tons of oocytes, can undertake
oocytes are large making them easily manipulated
Mice – mammalian homolog that has very similar development to humans
– cheap, grow fast, easily manipulated genetically, relatively small
genome (959 genes), relatively simple phenotypes (vulvaless, too many vulvas,
Chick – large embryo, easily manipulated, analogous to human development (germ
What are the 3 main germ layers and what tissues result from each?
Ectoderm – brain, nervous system, lens of eye
Mesoderm – skeletal system, gonads, muscles, outer coverings of internal organs
Endoderm – inner linings of gut, respiratory tract, liver, pancreas, thyroid
Give an example of a developmental program in bacteria
Bacteria usually simply divide equally into 2 cells but in response
to an environmental stimulus can divide asymmetrically.
Can create an inner (spore)
cell and an outer (mother) cell.
The mother cell provides an outer covering for the
spore so that it can protect itself from the environment and survive for millions of
What varies among cells/cell types?
Why is this
The nucleus among cells is equivalent, genetic material in all cells is identical.
However, the proteins and the RNAs that the nucleus encodes for generates varying
cytoplasmic environments that can potentially distinguish one cell from another.