http://www.buyartsuppliesonline.org/green-mosaic/
Genetics...regarding pea plants?
In the garden pea, orange pods (orp) are recessive to green pods (Orp), and sensitivity mosaic virus (mo) is recessive to resistance to the virus (Mo) A plant with orange pods and sensitivity to the virus was crossed to a true breeding plant with green pods and resistance to the virus. The F1 plants were then test crossed to plants with orange pods and sensitivity to the virus. The following results were obtained.
160orange pods, virus sensitivity
165green pods, virus resistance
36orange pods, virus resistance
39green pods, virus sensitivity
A. Conduct a chi square analysis to see if the genes are linked.
B . If the genes are linked, calculate the map distance between the two genes.
P: oomm x OOMM
F1: OoMm
new mating is OoMm x oomm
expected phenotypic ration is 1:1:1:1
total number of offspring is 400
expected numbers for each phenotype is 100.
A. Chi square is sum of ((obs-exp)^2)/exp
So, ((165-100)^2)/100 + ((39-100)^2)/100 + ((36-100)^2)/100 + ((160-100)^2)/100 = 156.42, which, with 3 degrees of freedom, gives a p value << 0.001 and therefore your observed are significantly different from expected.
B. map units is the percent recombination
The two recombinant classes are the green, virus sensitive and the orange, virus resistant groups.
So, ((36+39)/400)*100 = 18.75%. Therefore, the genes are 18.75 map units apart.
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