In a fruit fly (Drosophila melanogaster)family, alleles aer, brt and cts are all homozygous in recessive somatic cells. The 3 loci of aer. brt and cts are linked in order. Crossing the female flies of this family with male wild-type fruit flies, and make F1 heterozygous individuals intercross, the F2 are produced as follows:
+ + + 4365
aer brt cts 1168
aer brt + 278
+ + cts 269
aer + + 150
+ brt cts 141
aer + cts 16
+ brt + 13
(1)Please analyse and calculate the recombination frequency between aer and brt and that between brt and cts.
(2)How much is the coefficient of interference
参考答案：(1)杂交结果，F1为杂合体(+++/aer brt cts)。
雄果蝇中同一条染色体上基因百分之百连锁，所以F1杂合体相互杂交中，雄果蝇只产生两种类型的配子+++和abc。雌果蝇染色体上基因是部分连锁的，可产生8种配子。雄果蝇的配子+++与雌果蝇的任何配子结合，后代为野生型。雄果蝇的配子aer brt cts与雌果蝇的8种配子结合，后代的表型比代表着雌果蝇的配子比。F2代6400只果蝇中的3200只是雌果蝇染色体亲本型和连锁交换型对应的后代，在重组率的计算中，+++应记为4365-3200=1165。
重组率(recombination frequency)计算：
(2)
理论双交换值=10%×18%=1.8%
干涉系数(the coefficient of interference)=1-并发系数=0.5