Mosaic Analysis; the making of marked clones

1. Single versus twin spot mosaics

2. How they arise

   1. Spontaneously

      1. Usually very rare

      2. Ring-X chromosome of Drosophila - In(1)w^vC

      3. In C. elegans the loss of a free duplication

   2. Induced

      1. X-ray or γ-ray (essentially the same) - breaks chromosomes

Factors affecting clone size and frequency

1. Time of the event

2. Frequency

3. The choice of markers (a and b)

4. Time of action of the gene is important - perdurance

What do mosaics tell us

1. Descendants of a cell

2. Where a gene acts - Cell autonomy

3. Fate mapping with gynandromorphs

Examining gene expression

1. RNA

   1. In situ hybridization

   2. Promoter fusions

      1. LacZ - β-galactosidase

      2. GFP

2. Protein

   1. Antibody

   2. Protein fusions of LacZ and GFP