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Drosophila life cycle

Rearing flies Fly cultures are most successful if they are kept near 21 ˚C. Larval development is faster at 25 ˚C but harmful fungi, bacteria, and mites often kill cultures at these temperatures. It’s a good idea to check the cultures every few days; you may have to start them over if the population becomes infected. After about 6 days the parents should be removed. Counts—The Observed Results Within 14–16 days after the cultures have been started, the offspring will begin to emerge. It’s best to anesthetize, sort, and count the newly emerging adults every-other-day, or so, over the 10-day emergence period. Careful records should be kept of the counts; data sheets are provided at the end of this lab exercise for this use. Fundamental Genetics—The Predicted Results This section provides an overview of some basic concepts in genetics with an emphasis on the inheritance of traits in fruit flies. Additional information will be given in the lab lecture, the lecture course, and is available in Campbell (1996; chapters 12–14). Normal + wild type Spineless-aristapedia ssa antennae enlarged and leg-like Wings: Normal + wild type Vestigial vg wings reduced Apterous ap wingless Dumpy dp wings truncated Bristles: Normal + wild type; long Singed sn short and curled spineless ss short and fewer Body color: Normal + tan Yellow y yellow Ebony e dark brown TABLE 27. Abbreviations and descriptions of various common phenotypes. Phenotype Abbr. Description Mendelian Genetics: Lessons from the Fruit Fly 88 BS/LBS 158H Drosophila Notation Workers using fruit flies for genetics studies have devised a somewhat standard shorthand method for designating genotypes and phenotypes. You were already introduced to some of this notation in the Phenotype section above, but here it will be treated more extensively. First, normal wild-type flies or a single wild-type allele is designated with a “+”, and other alleles are given an abbreviation (a list of common phenotypes and their abbreviations are given in a table above). Abbreviations beginning with a lower case letter indicate the trait is recessive (e.g., “w” for white eyes and “y” for yellow body), whereas those beginning with an upper case letter (e.g., “B” for bar eyes) are dominant alleles. A fly’s genetic condition can be further designated as to whether or not a particular set of traits are linked. Those that are linked are joined by an underlined, and those not linked have separate underlining. For example, the notation “y v f” denotes these three alleles occur on the same chromosome; however, “y v e” shows that “y” and “v” are on one chromosome and “e” is on another chromosome. The notation can also be used to show homozygous and heterozygous conditions. For example, shows all three traits are linked and heterozygous; this individual’s phenotype would be wild type because all the mutant alleles are recessive.