If the genes are linked on the same chromosome, there would be two phenotypes in the F2 progeny. If the genes are on different chromosomes, there would be four phenotypes in the F2 progeny: the two parental phenotypes and two new recombinant phenotypes. The document then discusses a test cross between heterozygous long day flowering plants. The expected ratio for F1 offspring is 3 long day: 1 short day. This follows Mendelian inheritance patterns for a dominant long day allele.

1. If the dpy-11 and unc-31 genes are linked on the same chromosome, how many phenotypes
would the F_2 progeny show? If the two genes are on different chromosomes and therefore
independently assorting, how many phenotypes would you see in the F_2 worms? List the
phenotype(s). Strawberry plants have varieties that flower when the days are still short, and
other varieties that flower only when the days get longer. The long-day allele is dominant to the
short-day allele. You'd like to test whether or not this gene is inherited in a Mendelian fashion.
When you cross between heterozygous plants and count the offspring in the F_1 generation, this
is what you find: 85 plants with no flowers on short days and 35 plants with flowers on short
days What would you expect the ratio of phenotypes be? What is your Chi squared value?
Show your work What does this mean?
Solution
2. Linked genes tend to inherit together for the next-generations. No crossing over ororoccurs
independent assortment occurs. No new characters appear. Where as gegenes are on different
chromosomes, they are non linked. Crossing over or independent assortment takes place. New
characters appear along with parental characters. So dpy-11 & unc-31 present on same
chromosome, they are linked and give only parental characters. Only 2 phenotypes appear. If the
said genes present on different chromosomes, they give 4 different phenotypes
3. a. Heterozygous long day representing as Ll. When crossing or hybridization occur between
these genes
Ll x Ll ----------> 3:1 is the phenotypes ratio. Three are long and one is short.
Chi square value can be calculated by using the formula.
(O-E)^2/E
O = observed phenotypes; E = Expected phenotypes