Homework Sourse6 Question 516 Flies from a Dichaete stock are crossed to ho
#6 Question 5.16 Flies from a Dichaete stock are crossed to homozygous ebony, pink flies, and the F1 progeny, with a Dichaete phenotype, were backcrossed to the ebony, pink homozygotes.
Phenotype Number
Dichaete 401
ebony, pink 389
Dichaete, ebony 84
pink 96
dichaete, pink 2
ebony 3
Dichaete, ebony, pink 12
wild type 13
Identify which categories are noncrossovers (NCO), single crossovers (SCO), and double crossovers (DCO) in each case. Then, indicate the relative frequency in which each will be produced.
Solution
P= D + +/ + + + (Dicahete) X + e p/ + e p (homozygous ebony, pink)
F1= D + +/ + e p (Dicahete) X + e p/ + e p(homozygous ebony, pink)
F2 progeny
Phenotype
Genotype
Number
Type of crossover
Dichaete
D + +/ + e p
401
Parental combination or non-recombinants
Ebony, pink
+ e p/ + e p
389
Parental combination or non-recombinants
Dicahete, ebony
D e +/ + e p
84
Single crossover
Pink
+ + p/ + e p
96
Single crossover
Dichaete, pink
D + p/ + e p
2
Double crossover
Ebony
+ e +/ + e p
3
Double crossover
Dichaete, ebony, pink
D e p/+ e P
12
Single crossover
Wild type
+++/ + e p
13
Single crossover
Crossover frequency between D and p= Number of recombinant progeny/total progenyx100= (12+13+2+3/1000)x100=3 map units
Crossover frequency between p and e= Number of recombinant progeny/total progenyx100= (84+96+2+3/1000)x100=18.5 map units
Based on the results obtained in double crossover we can say that the genotypes of parents in F1 cross is
F1: D + +/ + p e X + p e/ + p e
| Phenotype | Genotype | Number | Type of crossover |
| Dichaete | D + +/ + e p | 401 | Parental combination or non-recombinants |
| Ebony, pink | + e p/ + e p | 389 | Parental combination or non-recombinants |
| Dicahete, ebony | D e +/ + e p | 84 | Single crossover |
| Pink | + + p/ + e p | 96 | Single crossover |
| Dichaete, pink | D + p/ + e p | 2 | Double crossover |
| Ebony | + e +/ + e p | 3 | Double crossover |
| Dichaete, ebony, pink | D e p/+ e P | 12 | Single crossover |
| Wild type | +++/ + e p | 13 | Single crossover |
