Basics of Drosophilia Genetics Basic Fly Anatomy Male

Basics of Drosophilia Genetics

Basic Fly Anatomy

Male and Female Fly

Fly Morphology

Female Male

Defining Important Terms Karyotype Sex Chromosome XX, XY Gene Locus Allele Phenotype Genotype

• • Wild Type Mutant Type Homozygous Heterozygous Hemizygous Dominant Recessive

Karyotype

Meiosis Overview **An important feature in fly genetics is the total absence of recombination in males **Balancer Chromosomes control recombination in females (to be discussed later)

Meiosis I

Meiosis II

Monohybrid Cross

Female Fly and Virgins

The Naming Game • The best way to study a gene is to mutate it and see what happens when the gene’s function is lost. As a result, genes are usually named after the phenotype caused by the mutation. • The white gene, which codes for eye color. Flies with a normal version of the white gene (usually written as w+ ) actually have red eyes, while flies with a mutation in the white gene ( w– ) have white eyes. • The name and symbol are capitalized if the phenotype of the mutant allele for which the gene was named is dominant to a wild -type allele.

Mutants to Identify

Normal Wildtypes These normal fruit flies, or "wildtypes, " have black-and-tan striped bodies. Compare them with the other fruit flies here.

Yellow Flies Notice that these flies are yellower than normal flies. They have a defect in their "yellow gene, " which is on the X chromosome. Since the yellow gene is needed for producing a fly's normal black pigment, yellow mutant flies cannot produce this pigment. y

Ebony Flies Notice that these flies have a dark, almost black, body. They carry a defect in their "ebony gene, " on the third chromosome. Normally, the ebony gene is responsible for building up the tan-colored pigments in the normal fruit fly. If the ebony gene is defective, the black pigments accumulate all over the body. e

White Flies These flies have white eyes. They have a defect in their "white" gene, like orange-eyed flies. But in these flies, the white gene is totally defective: it produces no red pigment at all. w

Curly Wing

Lobed Eyes v Normal L

Stubble Sb

Examples of ‘Funny’ Gene Names • • • Cheapdate– mutants have decreased resistance to the effects of alcohol Hangover– mutants can’t develop a tolerance for alcohol Dunce– mutants have learning deficits Tinman– This gene regulates the development of a heart, so flies with a mutation in this gene can’t grow a heart. Named after the character in Wizard of Oz Ken and Barbie – mutants do not develop external genitals Swiss cheese – mutants have holes in their brain I’m not dead yet – mutants live twice as long as normal flies, a reference to Monty Python and the Holy Grail Groucho Marx – mutants develop an excess of facial bristles Out Cold – mutants lose coordination at cold temperatures Clumsy – mutants have trouble walking