1. Symbols to Know for Crosses
a/a – a is the allele and / represents the two chromatids – there are two alleles for a diploid organism
a b/a b – two different genes on the same chromosome
a/a ; b/b – two different genes on different chromosomes ; designated separate chromosomes
X – symbolizes mating between two different individuals
X - symbolizes a self cross – when the hermaphrodite worms fertilize their own eggs
+ is the wild type or non-mutant form of a gene

2. Creating a heterozygous male
Male Parent
genotype
Hermaphrodite
Parent genotype X
Female gametes
Male gametes
Progeny genotype
Progeny phenotypes
and ratios
Which progeny are you continuing with? Why?

3. Linkage 1: Cross with Unlinked unc
Male Parent
genotype
+/+ ; unc/unc
Hermaphrodite
Parent genotype X
Female gametes
Male gametes
F1 Progeny genotype
and ratios
F1 Progeny phenotypes

4. Linkage 2: Selfing of hermaphrodite from unlinked crossX
self cross
gametes
Progeny genotype
Progeny phenotypes
and ratios

5. Linkage 1: Crossing with Linked unc
Male Parent
genotype
+ unc/ + unc
Hermaphrodite
Parent genotype X
Female gametes
Male gametes
Progeny genotype
Progeny phenotypes
and ratios
Which progeny are you continuing with? Why?

6. Linkage 2: Selfing of hermaphrodite from linked crossX
self cross
gametes
Progeny genotype
Progeny phenotypes
and ratios

7. Mapping 1: Making the double mutant
hermaphrodite X
self cross
gametes
Progeny genotype
Progeny phenotypes
and ratios
What if the genotype of the parent was + unc/+ unc?

8. Mapping 2: Making heterozygotes for mapping
Male Parent
genotype
Hermaphrodite
Parent genotype X
Female gametes
Male gametes
Progeny genotype
Progeny phenotypes
and ratios
Why might you see Dpy Unc progeny?

9. Mapping 3: Test Cross Hermaphrodite Male Parent Parent genotypeX
Parental
Recombinant
Female gametes
Male gametes
Progeny genotype
Progeny phenotypes
and ratios