Development of Drosophila melanogaster

By: Madolyn Mae Marin

Larva and Pupal stages

Exhibits Complete Metamorphosis

Fruity Fly Egg and Larva

larval instars

Larval stage of Drosophila consists of three Instars:

o 24 hours of hatching,larva molts to develop into 2nd instar

larva. o 48 hours 0f hatching,

2nd instar larva molts and matures to 3rd instar larva.

During these molting stages:

the larva loses its spiracles, mouth and hooks.

feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself.

larva’s task is to feed voraciously and molts when covering can’t accommodate the growing body size.

Imaginal disks

committed to form key parts of adult fly. grow inside the larva. cells of the imaginal disks are set aside

during embryogenesis and continue to grow and divide during the larval stages.

Remains undifferentiated.

IMAGINAL DISCS CELLS

Polytene Chromosomes

• As the fly larva grows, it keeps the same number of cells, but needs to make much more gene product.

• Cells get much bigger and each chromosome divides hundreds of times, but all the strands stay attached to each other.

• The result is a massively thick polytene chromosome.

• Pattern of dark and light bands, which is unique for each section of the chromosome.

• As a result, by reading the polytene bands, you can see what part of the chromosome you are looking at.

• Any large deletions, or other rearrangements of part of a chromosome can be identified, and using modern nucleic acid probes, individual cloned genes can be placed on the polytene map.

Polytene Chromosomes

• Polytene chromosomes are usually found in the larvae, where it is believed these many-replicated chromosomes allow for much faster larval growth than if the cells remained diploid.

• Simply because each cell now has many copies of each gene, it can transcribe at a much higher rate than with only two copies in diploid cells.

Polytene Chromosomes

Polytene

Chromosomes

Larvae Transformed

Into Pupa

Metamorphosis

Pupae stage

• After 4 days of voracious feeding, the 3rd instar larva encapsulates itself inside a hard and dark colored puparium.

• Capsule made of hard secreted cuticle.• It is in this pupal stage, where the metamorphosis of

Drosophila melanogaster takes place, giving rise to wings and legs.

• In room temperature condition, the duration of metamorphosis lasts for 4 days.

Summary