Lab 2: Finish Series 1- Autosomal or Sex-linked?
- Examine each plate of F2 progeny. If you chose only L4 hermaphrodites, as instructed,you should only see hermaphrodite progeny. If you have a lot of males on your plates, you probably chose young adult worms rather than L4 hermaphrodite's. That's a problem - see your instructor.
- For each cross, you should count and examine a random sample of 100 worms. The mutant worms may be smaller and not move as well as the wild type worms. Look around your plate to get a quick assessment of the population.
- Record in your lab notebook the number of WT, Dpy, Unc, or Dpy Unc mutants by examining the phenotype as you remove each animal from the plate. (Be sure to flame the pick after removing each worm!!!) If the genes responsible for the mutations are unlinked, you should see WT's (+/+;+/+), Dpy’s (dpy/dpy;+/+), Unc’s(+/+;unc/unc) and Dpy Unc’s (d/d;u/u) in a ratio of 9:3:3:1. If linked, you should see a greater proportion than expected of Dpy Unc’s (d u/d u) double mutants vs Dpy or Unc single mutants among the mutant hermaphrodite progeny.
The main challenge is to correctly differentiate single mutants of each phenotype (Dpy or Unc) from double mutants(Dpy AND Unc). Students tend to undercount single mutants and overcount doubles when they are inexperienced. Check with your instructor if you are unsure about how to score these groups. WT worms may be undercounted because they are harder to "catch". Be careful not to skew your data in this way.
Make sure you copy your data into the appropriate place on the course spreadsheet on the middle computer in the back of the lab!
You should now be able to conclude which strain has mutations that are autosomal and linked, which strain has mutations that are both autosomal and unlinked, and which strain has an autosomal mutation and an x-linked mutation responsible for either the Dpy or Unc phenotype (which one?).
**See Assignments page for instructions on Series 1 Results section write up for this project. Due at the beginning of Lab 4.