Three recessive traits in garden pea plants are as follows: yellow pods are rece

Question

Three recessive traits in garden pea plants are as follows: yellow pods are recessive to green pods, bluish-green seedlings are recessive to green seedlings, and creeper (a plant that cannot stand up) is recessive to normal. A true-breeding normal plant with green pods and green seedlings was crossed to a creeper with yellow pods and bluish-green seedlings. The F1 plants were then crossed to creepers with yellow pods and bluish green seedlings. The following results were obtained.

2059            green pods, green seedlings, normal

             151            green pods, green seedlings, creeper

             281           green pods, bluish-green seedlings, normal

               15           green pods, bluish-green seedlings, creeper

          2041            yellow pods, bluish-green seedlings, creeper

             157           yellow pods, bluish-green seedlings, normal

             282           yellow pods, green seedlings, creeper

                11          yellow pods, green seedlings, normal

Construct a genetic map that describes the map distance between these three genes.

Explanation / Answer

Distance between gene for green pods and green seedling will be :-

Green pods and green seedlings is the parental type. Similarly, yellow pods and bluish green seedlings is also parental type. Now, green pods with bluish green seedlings (281+15 =296 ) and yellow pods with green seedlings (282+11=293) will be the recombinants.

Total =4997

No. of such recombinants = 293+296/total *100 = 589/4997 *100 ~11.78 mu

Similarly, calculating Distance between gene for green seedling and normal will be

Normal, green seedlings is the parental type. Similarly, creeper and bluish green seedlings is also parental type.

Now, normal with bluish green seedlings (281+157 = 438 ) and creeper with green seedlings (151+282=433) will be the recombinants.

871/4997 *100 = 17.43 mu~18mu

alculating distance between gene for green pods and normal

Green pods and normal is the parental type. Similarly, yellow pods and creeper is also parental type. Now, green pods, creeper (151+15 =166 ) and yellow pods, normal (157+11=168) will be the recombinants.

distance = 327/ 4997 *100 = 6.54 mu.

so, creeper_________6.54mu___________yellow pods______11.84mu____________bluish green seedlings

                                                (total distance ~18mu)

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