In tomatoes, spherical fruit shape is dominant to oblate, and tall is dominant t

Question

In tomatoes, spherical fruit shape is dominant to oblate, and tall is dominant to dwarf.

o = oblate, O = spherical d = dwarf, D = tall A

true-breeding oblate, tall strain is crossed to a true-breeding spherical, dwarf strain. The F1 generation is testcrossed to a true-breeding oblate, dwarf strain.

1,000 testcross progeny are produced as follows: 420 spherical, dwarf 100 spherical, tall 110 oblate, dwarf 370 oblate, tall

What is the genetic map distance between the two genes? How did you determine which were recombinant and which are non-recombinant? Explain your answer.

Explanation / Answer

Answer:

true-breeding oblate, tall strain(Od/Od) x true-breeding spherical, dwarf strain (oD/oD)----P1

Od oD ---------------------------------------------------------Gametes

Od/oD (oblate, tall)---------------------------------------F1

Od/oD gives two recombinant gametes, od & OD. These gametes give recombinant phenotypes or genotypes in test cross.

Recombination frequency = (no. of recombinant progeny / Total progeny)100

= (100+110 / 1000)100 = 21%

RF (%) = Map distance

So distance between the genes is 21 map units

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