Development
•Homework #2 is due
10/17
•Bonus #1 is due 10/24
So,
Smoking during pregnancy may have indirect
and/or direct affects on fetal development, and
these affects may manifest themselves in adults.
Correlation of weight and relatedness
Correlation of weight (BMI)
Biological siblings
Parents and children living together
Identical twins reared together
Identical twins reared apart
Fraternal twins reared together
Adopted children and parents
Unrelated children living together
%
34
26
80
72
43
4
1
Nature and Nurture:
Are traits coded for by genes fixed while traits
coded for by the environment are under our
control?
Developmental mutants of
Drosophila melanogaster
Fig 12.1
Vertebrate
Development:
from zygote to adult
Besides adding
cells, development
can involve cell
death.
Development of a mouse paw: yellow areas
show dying cells
CB 21.19
Early embryo development
Totipotent: ability to differentiate into any
cell-type
Totipotency is limited to early stages of animal
development
Mature,
differentiated plant
cells are totipotent
Why do cells lose totipotency?
Why do cells lose totipotency?
•Gene expression can be
controlled at many points
between DNA and making
the final proteins.
•Changes in the various
steps of gene expression
control when and how
much of a product are
produced.
Why change gene expression?
•Different cells need different
components
•Responding to the
environment
•Replacement of
damaged/worn-out parts
DNA packaging
fluctuates…
genes being expressed
are unpackaged, genes
not needed are tightly
packaged.
Normally DNA is loosely
packaged
During mitosis DNA is tightly
packaged as chromosomes and
individually visible
box 2.1
DNA packaging
fluctuates…
Some of the tight
packaging of DNA is
irreversible.
Irreversible
packaging
of DNA
partially
explains the
loss of
totipotency.
Stem cells still have totipotency
Embryonic Stem Cells
are totipotent
Adult Stem Cells are
pluripotent (only form
some cell types)
Developmental information can be encoded by
both genetic and non-genetic information.
Fig 12.2
What genetic mechanisms regulate/allow
development?
All humans
are female for
the first nine
weeks of
development
All humans
are female for
the first nine
weeks of
development
Down’s Syndrome is caused
by an extra chromosome 21.
Down’s Syndrome is caused
by an extra chromosome 21.
Too much information disrupts
normal development.
4 whorls of a flower
Flower parts:
Complexity from a
few simple genes
Each whorl expresses a specific
combination of three genes
CB 21.20
Changing expression
of A, B, or C genes
changes organ identity
CB 21.20
Development
•Homework #2 is due
10/17
•Bonus #1 is due
10/24