The genetics of axis specification in drosophila

Exam 2

Micropyle is the

Only site on the drosophila egg where sperm can enter

The micropyle allows

One sperm to pass through, prevents polyspermy

Syncytial blastoderm

Results from about 5 nuclei reaching posterior pole & become enclosed by cell membranes and these pole cells give rise to gametes of the adult

Syncytium

Single cell, many nuclei, before nuclei pushed to posterior pole

Cellular blastoderm

Nuclei reach the periphery of the egg causing cell membranes to for the

Gurken

Cytoplasmic protein of developing oocyte; product of Gurken a maternal effect gene

Gurken interacts with a receptor protein called

Torpedo on follicular cells surrounding the oocyte; signaling posteriorization of follicular cells

Torpedo

Receptor protein; Product of torpedo gene

Gap genes are

Among the earliest zygotic genes to be expressed; mutations in these genes cause gaps in segmentation patterns

Gap genes encode transcription factors that

Regulate transcription of pair-rule genes, diving embryo into periodic units of 7 transverse bands

Bicoid is the

Primary anterior morphogen in early embryo

Bicoid is a

Maternal effect gene

Bicoid mRNA is located near the

Anterior tip of unfertilized egg

After ovulation & fertilization Bicoid mRNA is

Translated into protein in anterior region of embryo

Nanos is a

Maternal effect gene

Nanos is the

Primary posterior morphogen in early embryo

Nanos mRNA is located near the

Posterior tip of unfertilized egg

After fertilization & ovulation Nanos mRNA is

Translated into protein in posterior region of embryo

Bicoid facilitates transcription of the

Hunchback gap gene in anterior region

Nanos inhibits translation of

Hunchback mRNA in posterior region

High levels of hunchback prevent

Transcription of the posterior gap gene knirps

Primary pair rule genes even-skipped & runt are

Expressed in 7 stripes

Even-skipped expressed →

Engrailed gene activated

Engrailed gene activated →

Hedgehog protein expressed

Engrailed is found in

14 strips across anterior-posterior axis of embryo

High levels of runt →

Engrailed repressed

Hedgehog protein expressed →

Expression of wingless

Antennapedia

Legs, 3rd thoracic segment

Abdominal A &Abdominal B

Abdominal segments, digestive stuff