In garden pea, resistance to a certain disease is controlled by a single locus with dominance for resistance (R) and recessive susceptible (r). Another locus governs seed color with yellow being dominant (Y) to green (y). A pea plant which is heterozygous for both gene pairs is crossed with a susceptible and green- seeded plant. The following data was observed in the progeny. Phenotype Number Resistant yellow 43 Susceptible green 49 Resistant green 16 Susceptible yellow 12 Total 120 a. What is the calculated chi-square value based on an independent assortment assumption? Compute for the df and write the conclusion. (NOTE: The cross will not yield a 9:3:3:1 ratio since not both of the parental genotypes are heterozygous for the 2 pairs of alleles. Thus, perform the cross first, show the parental genotypes, the gamete types that will be produced from the parents and the GR and PR (Phenotypic ratio). Use the computed PR in calculating the expected ratio/value. The observed ratio is given in the table above. b. Assuming linkage, which of the test cross classes are the results of crossing-overs? c. What is the map distance between these two loci? Show the computations.
In garden pea, resistance to a certain disease is controlled by a single locus with dominance for
resistance (R) and recessive susceptible (r). Another locus governs seed color with yellow being dominant (Y)
to green (y). A pea plant which is heterozygous for both gene pairs is crossed with a susceptible and green-
seeded plant. The following data was observed in the progeny.
Resistant yellow 43
Susceptible green 49
Resistant green 16
Susceptible yellow 12
Total 120
a. What is the calculated chi-square value based on an independent assortment assumption? Compute for
the df and write the conclusion. (NOTE: The cross will not yield a 9:3:3:1 ratio since not both of the
parental genotypes are heterozygous for the 2 pairs of alleles. Thus, perform the cross first, show the
parental genotypes, the gamete types that will be produced from the parents and the GR and PR
(Phenotypic ratio). Use the computed PR in calculating the expected ratio/value. The observed ratio is
given in the table above.
b. Assuming linkage, which of the test cross classes are the results of crossing-overs?
c. What is the map distance between these two loci? Show the computations.
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