Getting to know Drosophila melanogaster RS: Maribel Alvarez Nelida Rojas, Santa Ana High School _Alvarez/Welcome.html Arora Lab

Presentation Outline Introduction to Drosophila melanogaster. Station 1: Identify the different stages of Drosophila development. (week 1) Station 2: Identify males versus females. (week2) Station 3: Flying through genetics. (week 3) Station 4: Gene expression, function, and regulation. (week 4)

Drosophila Melanogaster, a popular genetic model organism ~ 50% of fly genes have vertebrate homologs. Small and easy to grow in lab. Short life cycle. Produce high amounts of offspring.

Drosophila Melanogaster is used to study the biological processes underlying: Embryonic development Neurodegenerative disorders Diabetes Aging Drug abuse Cancer

Station 1: Identify the different stages of Drosophila development The life cycle of Drosophila melanogaster

Station 1: Identify the different stages of Drosophila development The egg: Eggs are small, oval shaped, and have two filaments at one end. The larval stage: The larva look like worms. They use black mouth hooks to eat. Three larval stages. The pupal stage: A pupa undergoes four days of metamorphosis. They form a hard and dark pupal case. The adult stage: Adult flies have a head, thorax, abdomen, six legs, and two wings. They live a month or more and then die. A female does not mate for hours after emerging from the pupa.

Station 2: Identify males versus females 1. Size of adult The female is larger than the male. 2. Shape of abdomen The female abdomen curves to a point; the male abdomen is round 3. Markings on the abdomen Alternating dark and light bands can be seen on the entire rear portion of the female; the last few segments of the male are fused. 4. Appearance of sex comb On males there is a tiny tuft of hairs on the front legs. 5. External genitalia on abdomen Located at the tip of the abdomen, the ovipositor of the female is pointed. The claspers of the male are darkly pigmented, arranged in circular form, and located just ventral to the tip. sex comb

Is this a female or male? This is a virgin female. In genetic experiments, it is important that the female be a virgin in order to determine genetic background of progeny.

Station 3: Flying through genetics Humans are diploid organisms (2n) Humans have 23 pairs of chromosomes

Station 3: Flying through genetics Mendel ’ s law of segregation states that during gamete formation the pair of alleles segregate so that each gamete only gets one allele

Station 3: Flying through genetics Drosophila is a diploid organism (2n) Female Male XX /XYII III IV Autosomal Sex

Station 3: Flying through genetics To study the basic genetic principles of mendelian inheritance a cross has been set up between male flies that have Curly (Cy) wings and a wild-type virgin female flies with straight wing (Cy + ). Cy is a dominant trait.

Station 3: Flying through genetics

Station 4: Gene expression, function, and regulation The development and growth of an organism is greatly dependent on the proper expression of genes

Gene Expression

Station 4: Gene expression, function, and regulation All cells have the same genetic information however only specific genes are turned on or expressed in each cell type

Gene Expression Organisms need genes expressed in specific cells at the right time. Gene expression must be regulated for proper growth and development of organisms

Station 4: Gene expression, function, and regulation 1.What would happen if the neuron specific gene is not expressed in cell one? 2. What would happen if the neuron specific gene was expressed instead of the epithelial specific gene in cell 2? The cell that was suppose to be an epithelial cell would be a neuronal cell. No neuron 1.2.

Station 4: Gene expression, function, and regulation ? We will study the function and expression of eyeless (ey), a gene responsible for making eyes in Drosophila.

Station 4: Gene expression, function, and regulation ey is expressed in the larval eye disc, which develops into the adult eye.

Station 4: Gene expression, function, and regulation How do we study gene expression? eyeless promotor eyeless gene eyeless promotor Reporter: GFP or LacZ

Station 4: Mutations affecting gene expression We have altered the expression of ey in flies found in vials 2 and 3. Observe and record their phenotypes.