The bacterial DnaA protein is the replication initiator; it binds sequence specifically to multiple sites (dnaA boxes) in oriC.

#Id: 3799

#Unit 5. Developmental Biology

Dictyostelia (social amoebas)

#Id: 3800

#Unit 5. Developmental Biology

Dictyostelium can utilize one of three survival strategies when food starvation-

Microcyst formation, favoured in dark & wet conditions, or ammonia levels are high.

Zygote formation, favoured in dark & wet conditions, & is triggered by ethylene produced by the cells. 

Cell aggregation & differentiation

#Id: 3801

#Unit 5. Developmental Biology

Cell Aggregation & Differentiation is common to all Dictyostelids.

It consists of an interconnected programme of cell movement and cell differentiation.

#Id: 3802

#Unit 5. Developmental Biology

During growth, unicellular D. discoideum monitor their cell density relative to that of their bacterial food source by secreting a glycoprotein called prestarvation factor at a constant rate.

#Id: 3803

#Unit 5. Developmental Biology

When the ratio of PSF relative to that of bacteria exceeds a certain threshold, cells stop proliferating and initiate the expression of genes that are required for their aggregation.

#Id: 3804

#Unit 5. Developmental Biology

Early on during aggregation, gene expression requires the activity of cAMP-dependent protein kinase.