Assignment: McCourt Section
1. You have decided to do some genetic analysis on an earthworm species that is diploid. You identify a homozygous mutant that is much longer than the normal wild type worm. You call the mutation that causes this long mutant worm phenotype, Lon. You cross a true breeding Lon mutant to wild type and all the F, worms are long. When you allow the F, worms to self and produce Fa worms they segregate as follows:
|
Phenotype
|
Number
|
|
Wild type length
|
150
|
|
Long
|
392
|
What is the genetic nature of the Lon mutation (genetic nature means is the Lon mutation dominant or recessive)
How do you know this? (you must use statistical analysis for your answer)
2. You decide to do a supressor screen on a true breeding homozygous Lon mutant to find more genes in the pathway. You find two suppressor of the Lon mutation (Supl and Sup2) that result in wild type worms. You cross the Lon Supt line to a line homozygous for the Lon mutation and all the F, progeny are phenotypically long. After allowing the Fr worms to self, you see the following numbers in the Fa progeny:
|
Phenotype
|
Number
|
|
Wild type length
|
240
|
|
Long
|
677
|
a. What is the genetic nature of the Sup1 mutation?
b. Is the SUP1 gene genetically upstream or downstream of the LON gene? How do you come to this conclusion? Your answer must include genotypes.
3. Next, you look at your Lon Sup2 suppressor line. You are about to genetic analysis on it when you notice that if you simply allow this line to self and propagate, progeny from the next generation shows the following:
| |
Table 1
|
|
|
Phenotype
|
Number
|
Genotypes |
|
Wild type length
|
794 |
|
|
Long
|
390
|
|
You decide to look more closely at this population and you find that some worms from your soiled line were never born and die as embryos. These dead embryos are found in the same numbers as the Long phenotypic class of mutant worms seen in Table 1. When you cross a homozygous Lon mutant to your original Lon Sup2 line that you identified you find the following in the next generation:
|
Table 2 |
|
|
Phenotype
|
Number
|
Genotypes |
|
Wild type length
|
288
|
|
|
Long
|
279 |
|
And there are no dead embryos.
a. What is the genetic nature of the Sup2 mutation Your answer must include filling in Genotypes column of Table 1 and Table 2?
b. Propose a signaling pathway model to explain the nature of the Sup2 suppressor. Your answer should show the genetic relationship between LON and SUP2 in wild type, each single mutant and double mutant worms so you will need to draw four pathways.