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

Series 1: Autosomal Unlinked

Hermaphrodite Parent genotype

Male Parent genotype X

Male gametesHermaphrodite gametes

F1 Progeny genotypes

Which progeny are you continuing with? Why?

F1 Progeny phenotypesand ratios

+/+ ; +/+ dpy/dpy; unc/unc

Series 1: Autosomal Unlinked

F1 parent

X self cross

F1 gametes

F2 Progeny genotype

F2 Progeny phenotypes and ratios

students can show Punnet Square

Series 1: Autosomal Linked

Hermaphrodite Parent genotype

Male Parent genotype X

Male gametesHermaphrodite gametes

F1 Progeny genotype

Which progeny are you continuing with? Why?

F1 Progeny phenotypesand ratios

+ + / + + dpy unc/dpy unc

F1 parent

X self cross

F1 gametes

F2 Progeny genotype

F2 Progeny phenotypesand ratios

Series 1: One Autosomal, One x-linked

Hermaphrodite Parent genotype

Male Parent genotype X

Male gametesHermaphrodite gametes

F1 Progeny genotype

With which progeny are you continuing? Why?

F1 Progeny phenotypesand ratios

+/+ ; +/0gene-1/gene1; x-gene2/x-gene2

F1 parent

X self cross

F1 gametes

F2 Progeny genotypes

F2 Progeny phenotypesand ratios

Series 1: One Autosomal, One x-linked