TS 2 Flashcards
How many segments are in the abdomen region?
8
How many segments are in the thorax region?
3
At what cycle is the syncitial blastoderm?
10-12
At what cycle is celularization?
13+
At what cycle is segmentation?
14
What is a dentricle?
These hair-like follicles that are present in the ventral side segments and they point posteriorly
What are the naked regions?
These are the posterior segments that are in between the dentricle containing segments that lack dentricles
What is forward genetics?
This is a phenotypic driven process where a gene is mutated and the phenotype is observed then the gene responsible is determined
How was forward genetics conducted in flies?
- Adult male flies mutated using EMS
- The mutated gametes were crossed with WT female flies
- The mutated progeny (1000s of them) were observed
What was the mutant phenotype?
- Same number of segments
- Deleted naked regions
- Mirror duplicated dentricles
How did they know the dentricles were mirror duplicates?
Further posterior there were dentricles (duplicate) but they were pointing anterior (mirror)
What is a homolog?
Genes that relate because they possess an ancestral similiarity but then they differ due to a speciation
What is a paralog?
Ancestral genes with 2 duplicates in the genome that accumulate mutations
How do you determine homology?
With a DNA probe from a known gene
What is high stringency?
When the complementary DNA sequence has to be perfect for the probe to bind
What is low stringency?
When the complementary DNA sequence can be imperfect and the probe can still bind
What is the ZPA?
The zone polarizing activity is a signalling centre and is the source of a morphogen responsible for the patterning of the limb so, it is the area of the limb that secretes the morphogen
The identity of the ZPA morphogen was unknown so where did they start?
Looking for Drosophila HH as a homolog for patterning in the body segments in the chick since the HH was a secreted morphogen