Biochemistry - Drosophilia Genetic Control Flashcards
How can gene-differentiation interactions be identified?
Studying abnormalities
Early stages of development in drosophilia…
The Earliest stages of development are done-so in the oocyte, where mutations can affect development plan, being maternal-effect genes
Maternal Genes
Genes whose product are produced or deposited into the oocyte.
Where are zygotic genes important?
Embryo functioning developmental genes
What do zygotic genes do?
These interpret/respond to the positional information laid out in the egg by the maternal-effect gees
Pattern in drosophilia.
Segementation of 14 denticles, marking the basic insect body plan of 3 thoraic segments, 8 abdominal segments and three head segments
Parasegments
Consist of posterior region of one segment and the anterior region of another.
Four types of segmentation genes…
Co-ordinate Genes
Gap genes
Pair-rule genes
Segment-polarity genes
Co-Ordinate Genes
Determine co-ordinate axis of the embryo, that is the anterior-posterior axis and the dorsal-ventral axis.
How do the co-ordinate genes define the axis?
Polarity and gradients
What is anterior/head and thorax formation regulated by?
Bicoid gene
Bicoid Genes
Morphogens control embryonic gene expression by transcriptional activation and translational repression.
What is the product of the bicoid gene?
A TF for anterior-structure genes, produced by nurse cells, exported to anterior region of the oocyte
Mechanisms of bicoid…
Helix-turn-helix domain invades the DNA grooves, the genes activated containing upstream regions.
How can bicoid be regulatied?
Differences in two nucleotides can regulate bicoid affinity
What do the posterior genes affect?
The abdomen
What do terminal genes affect?
The most posterior and most anterior like the torso gene.
Gap Genes
Code for variour TF that form short-ragne morphogenic gradients, establishing next level of spatial organization.
What are gap genes function?
Defined by because mutations result in absence of pattern elements derived from contigous segments
Example of a gap gene…
Hunchback gene
How is hunchback expression is controlled?
When the effects of bicoid and nanos genes are offset
Function of Nanos…
Repress activation of bicoid, establishing an anterior-posterior gradient.
Pair-Rule Genes
Seperate the embryo into segments
Function of pair-rule genes…
Distinguish segmentation in the larvae, wiwth repetetiveness and indivdiually of the segments…
Example of pair-rule gene…
Hairy gene
Hairy gene
The earliest expressed, positvely/negatively regulated by hunchback/lruppel and other gap genes
Segment-Polarity Genes
Determine anterior-posterior axis development pattern
Function of the segment-polarity gene
They create spatial differentiation within each segment…
Example of segment-polarity genes…
The engrailed gene, dividing segments into anterior/posterior divisions.
What do imaginal disks in metamorphis form?
Tissues and structures
Example of imaginal disk structures?
Haltere wing disks
What does ecydosone in pupal stage regulate?
Break down of larval tissues/organs
Homeotic Genes
Give rise to identity of the segments, not producing any segments
Mutations in homeotic gene…
Cause tranformation into irrelevant structures…
Example of homeotic mutation?
Bithorax where the third thoracic segment into the anterior fo the second thoracic segments results in haltere forming an ADDITIONAL pair of wings.
Function of HOX genes?
Control differentiation in many organisms of the nervous system, musculature and skeleotns.
Example of the HOX gene conservation…
PAX6 gene which has identifcal amino acid sequneces in humans and mice AND drosophilia.
What is PAX6 foudn in?
Planarians, octopus, vertebrates and insect compound eyes.
