Transcript MATH 499 VIGRE Seminar: Mathematical Models in Developmental

MATH 499 VIGRE Seminar:
Mathematical Models in Developmental
Biology
Drosophila development 101
Fruit fly lifecycle
Beginning
Anterior-Posterior Axes Specification
Maternal mRNAs
a) Nurse cells deposit
mRNAs into
oocyte
b) Bicoid mRNA localized
at anterior,
nanos at
posterior
c) Bicoid mRNA
translated
and forms
protein
gradient from
anterior to
posterior
d) Nanos mRNA
translated
and forms
posterior to
anterior
protein
gradient
e) Hunchback and caudal
Translation
a) Hunchback mRNA
translation suppressed in
posterior by nanos
b) Bicoid acts as
transcription factor to
activate hunchback
translation
c) Bicoid represses
caudal translation
d) Hunchback and
caudaul form opposing
gradients, with that of
hunchback being
strengthened by bicoid
Gap-genes
a) Gap genes are
activated/repressed by
maternal effect genes
b) Gap genes and their
products interact to
sharpen expression
boarders
c) Embryo is diveded
into unique domains
Pair-rule genes
a) Protein products of
gap genes interact with
their neighboring gap
gene’s proteins to
activate transcription of
pair-rule genes
b) Pair-rule genes
expressed in seven
stripes
c) Defines 14
parasegments, altenating
between pair-rule
expression and none
Segment-polarity genes
a) Segment polarity
genes act to define an
anterior and posterior part
of each parasegment
Experimental Evidence
1. Loss of gap gene results in a reduced number of segments as
shown in the embryo to the right.
2. Loss of a pair rule-gene, e.g. even-skipped, allows only oddnumbered segments to develop.
3. Loss of a segment polarity-gene leads to segments with similar
head and tail ends.
Even-skipped, Eve