Tutorial 6 linkage - Problems for tutorial 6 Name St 1 In...

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Problems for tutorial 6 Name St#____________ 1. In tomatoes, red (R) color is dominant to yellow (r) color and cut leaf (C) is dominant to potato leaf (c). A pure strain of red color, potato leaf plant is crossed to a yellow color, cut leaf plant and the F1 was test crossed to a yellow color, potato leaf plant which yielded the following progeny. 250 red color, cut leaf 247 yellow, potato leaf 256 red color, potato leaf 262 yellow color, cut leaf a) What ratio would you expect from a dihybrid test cross if the genes were assorting independently? 1:1:1:1 b) What statistical test would you use to test this ratio? chi-square test c) Is it necessary to use this test for this data? Why not? No, the ratio is close. d) What is the relationship between these loci? The genes do not show linkage. e) Diagram the cross (give genotypes for the parents, F1 and test cross progeny) Parents red, potato (R/R ; c/c) x yellow, cut (r/r ; C/C) F1 test cross red, cut (R/r ; C/c) x yellow, potato (r/r ; c/c) Test cross progeny 1 red, cut (R/r ; C/c) 1 red, potato (R/r ; c/c) 1 yellow, cut (r/r ; C/c) 1 yellow, potato (r/r ; c/c) 2) In tomatoes, tall (D) vine and spherical (O) fruit are dominant alleles of dwarf (d) vine and oblate (o) fruit. Two homozygous plants were crossed and the F1 was test crossed to a dwarf, oblate plant which yielded the following progeny. 406 tall, oblate 394 dwarf, spherical 93 tall, spherical 107 dwarf oblate a) Why isn't it necessary to use the Chi - Square test to see if these two genes are assorting independently? It is clear that this is not a 1:1:1:1 ratio. b) What is the relationship between these two genes? The genes are linked (or on the same chromosome) c) Diagram the cross (give genotypes for the parents, F1 and testcross progeny). (there are two possibilities for the parents. You should be able to tell which it is by looking at the test cross progeny) Parents ??? x ??? F1 test cross tall spherical ???? x dwarf oblate (d o/d o) test cross progeny Parental types — >> tall oblate (D o/d o), dwarf spherical (d O/d o), Recombinant types----->tall spherical (D O/d o), dwarf oblate (d o/d o) d) Even though you weren't told the exact genotype of the original parents (except that they were homozygous) and F1's you should note that is possible to determine it from the F2. Write them out with their correct phenotypes.
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