In the Balinese banana borer ( Quatrolium musadrilla ) cuticle color, spotting p
ID: 57047 • Letter: I
Question
In the Balinese banana borer (Quatrolium musadrilla) cuticle color, spotting pattern, and antenna length are controlled by separate loci each with a pair of alleles as follows: B (black cuticle) is dominant to b (brown cuticle); R (red spots) is dominant to r (orange spots); A (long antennae) is dominant to a(short antennae). These three loci are known to be syntenic in this species (you should know what this means – if not, look it up). F1 beetles were produced by crosses between two highly inbred and pure-breeding strains (strains 18 and 29) of this species. Strain 18 has black cuticle, red spots, and short antennae. Strain 29 has brown cuticle, orange spots, and long antennae. F1 females were then crossed to a third pure breeding strain (strain 10), which is brown, orange spots,
and short antennae, and the following offspring were recovered:
Phenotype
Black, red, short 347
Black, red, long 12
Black, orange, short 88
Black, orange, long 59
Brown, red, short 56
Brown, red, long 93
Brown, orange, short 14
Brown, orange, long 331
Give the relative order of the B, R and A loci and calculate the map distances between them (B to R, B to A, and R to A).
Explanation / Answer
Total number of offsprings = 347 + 12+ 88+ 59 + 56 + 93 + 14 + 331 = 1000
Map distance between B and R = 347 + 12 + 88 + 59 + 56 + 93 = 655/1000 = 0.655 m.u
Map distance between B and A = 347 + 12 + 88 + 59+ 93 + 331 = 930 / 1000 = 0.93 m.u
Map distance between R and A = 347 + 12 + 56 + 93 + 59 + 331 = 898 / 1000 = 0.898 m.u
Thus, the order of genes is B, R and A.