Punnett and a co-worker studied genetics in sweet peas. they found one gene that controlled purple(P) or red (p) flowers and another that controlled Long (L) or round (l) pollen. Parental true- breeding purple-flowered long-pollen plants were crossed with true-breeding red- flowered round - pollen plants. All progeny (F1) were purple-fowered long-pollen phenotypes. When the F1 progeny were self-pollinated, the results were 284 purple long; 21 purple round; 21 red long and 55 red round. from these data it appears that the two gene are linked, or perhaps that the alleles are not equally viable. the X2 (chi-square) test from statistics is useful for testing hypotheses we might have about experimental data. Let us test first the hypothesis that the alleles are equally viable and that they segregate independently . we list the observed (0) and experimental (E) number of each type in table 1
PL Pl pL pl
O 284 21 21 55
E
a)What is the total number of progeny counted and in what ration (ex, 3:1) would these progeny be if we assume that hypothesis that all progeny are viable and the allele segregate independently?
b)Fill the "E" data line with the numbers of each type that would be expected assuming the hypothesis correct (total of both O and E should be equal)
c) compute the X2 by finding for each type (O-E)2/E and summing up the results. Base on the value you compute for X2, would you reject the hypothesis? (chi-square distribution table). please state how many degrees of freedom you used.
d)what fraction of the total number of progeny are recombinant?
We formulate another hypothesis, that the alleles are equally viable; that half the recombinant are purple-flowered round -pollen and red- flowered long-pollen and half the non-recombinants (parental type) are purple -flowered, long-pollen and red-flowered round-pollen.
e)fill the E data line with the numbers of each type that would be expected assuming the new hypothesis is correct (totals of both O and E should be equal)
f)compute X2. would be reject the new hypothesis?
g) provide a brief interpretation of this date in regard to linked/non-linked and variable/non-variable genes.