Question

Drosophila may be monosomic for chromosome 4, yet remain fertile. A recessive mutant for bent bristles is identified on chromosome 4. Determine the genotypes of the F1 and F2 progeny for the following crosses.
The following cross is conducted of true-breeding adult flies: monosomic bent bristles x diploid normal bristles. Select the two F1 genotypes that will be produced from this cross
a. -/b+
b. -/b
c. b/b
d. b/b+
e. b+/b+

Answer 1

The answers are:
a. -/b+
d. b/b+

b+ - the allele for normal bristles
b - the allele for bent pristles

Monosomic means there is only one instead of two alleles in a gene locus.
So, the parents' genotypes are:
monosomic bent bristles: -/b
diploid normal bristles: b+/b+

The following cross is conducted of true-breeding adult flies:
Parents' phenotype: monosomic bent bristles x diploid normal bristles
Parents' genotype:                      -/b                   x              b+/b+
F1 generation:                       -/b+            -/b+                 b/b+            b/b+