The phenotypes seen in the offspring of this testcross are shown: Purple, long 4

Question

The phenotypes seen in the offspring of this testcross are shown:

        Purple, long 47
       Red, round     47
       Purple, round        3
       Red, long      3

0 Required information In pea plants, flower color is determined by gene P (Ps purple, p= red). Pollen shape is determined by gene L (L = long pollen;-round pollen). A plant heterozygous for the dominant purple allele and heterozygous for the dominant long pollen allele (L) is crossed with one that is homozygous recessive for both genes. Calculate the distance between genes Pand L in map units.

Explanation / Answer

Cross : PpLl X ppll

Gametes: PL , Pl , pL , pl pl

Offspring: PpLl (purple long) = 47

Ppll (purple round) = 3

ppLl (red long) = 3

ppll (red round) = 47

Here two are non parental combinations or recombinant (purple round and red long)

distance =( recombinant / total ) × 100 map unit

= (3+3 / 47 +47+3+3 ) ×100 = 0.06 × 100 = 6 mapunit.

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