Much of what we know about inheritance was first worked out in fruit flies and corn. Both let you watch real traits pass from parents to offspring, with no lab beyond a bench and a magnifier.
Drosophila melanogaster breeds fast, lives happily in a small vial, and comes in dozens of mutant strains with traits you can see.
It has four pairs of chromosomes. Pair 1 is the sex chromosomes, X and Y, so the same flies can show both ordinary and sex-linked inheritance.
These mutant strains are a common starting set because each trait is easy to spot under a stereo microscope or a hand lens.
A cross through two generations takes a little over five weeks, and warmer or cooler rooms shift the timing.
Counted flies are never returned to a vial, and they are not dumped in the trash alive either. Keep a jar of alcohol on the bench as a fly morgue and put every counted fly in it. Carolina's own labsheets list alcohol for exactly this.
Anesthetized flies wake up. A fly that walks out of the trash is a fly in your kitchen, and in a cross it is a contaminated result.
Tip old cultures into the morgue too, or bag and freeze the vial overnight before it goes out.
Cross white-eyed females with wild-type males. Every son inherits his X chromosome from his mother, so the sons have white eyes while the daughters have red eyes, a pattern you can see on the first day of counting.
A genetic corn ear is a whole Mendelian experiment already grown for you. Every kernel is one offspring, and its color and shape show which alleles it inherited.
Carolina's dihybrid ear comes from a cross of purple starchy (R/R Su/Su) with yellow sweet (r/r su/su) parents. On the second-generation ear the kernels fall close to 9 purple starchy to 3 purple sweet to 3 yellow starchy to 1 yellow sweet. Sweet kernels dry wrinkled, which makes them easy to tell apart.
Count one row at a time and mark your starting kernel with a pin. Kept dry, an ear lasts for years.
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Trinocular stereo zoom microscope on a double-arm boom stand, with a 144-LED ring light and Barlow lenses for 3.5X to 90X. The eyepiece tubes are 30 mm and the photo tube is 23 mm.
