The Drosophila chromosome 4 is extremely small; virtually no recombination occurs between genes on this chromosome. You have available three differently marked chromosome 4s: one has a recessive...

The Drosophila chromosome 4 is extremely small;
virtually no recombination occurs between genes on
this chromosome. You have available three differently
marked chromosome 4s: one has a recessive allele of
the gene eyeless (ey), causing very small eyes; one has
a recessive allele of the cubitus interruptus (ci) gene,
which causes disruptions in the veins on the wings;
and the third carries recessive alleles of both genes.
Drosophila adults can survive with two or three, but
not with one or four, copies of chromosome 4.
a. How could you use these three chromosomes to
find Drosophila mutants with defective meioses
causing an elevated rate of nondisjunction?
b. Would your technique allow you to discriminate
nondisjunction occurring during the first meiotic
division from nondisjunction occurring during the
second meiotic division?
c. What progeny types would you expect if a fly
recognizably formed from a gamete produced by
nondisjunction were testcrossed to a fly homozygous for a chromosome 4 carrying both ey and ci?
d. Geneticists have isolated so-called compound 4th
chromosomes in which two entire chromosome 4s
are attached to the same centromere. How can such
chromosomes be used to identify mutations causing
increased meiotic nondisjunction? Are there any
advantages relative to the method you described
in part (a)?