Why do individuals with an excessive number of sex chromosomes often show minimum phenotypes?

In the fruit fly Drosophila melanogaster, a recessive condition called eyeless (ey) significantly interferes with normal eye development. Eyes are either very small or absent. The ey gene is found on chromosome 4, which is the smallest of the four chromosomes in the organism. Individuals with a single copy or three copies of chromosome 4 are viable and can reproduce. A trisomic wild-type male is crossed with a disomic wild-type female: see attached image Determine the chromosome constitution and phenotypic ratios in the offspring. Assume random segregation of chromosomes into gametes.

For part c, do they consider the total sex chromosomes to be 2 or 3?

How does a chromosomal duplication occur?

In C. elegans, lon-2 and unc-2 are recessive mutations that are 8 map units apart on the X chromosome.  An hermaphrodite who is Lon and Unc is mated to a wild-type male.  An F1 hermaphrodite is mated to a wild-type male.  What are the expected percentages of the different phenotypes among the male progeny?

What kind of polymorphism is most likely represented?

In the classic "X" figure of the chromosome, is the whole X from one parent, or is one side of the X from the mother and the other side from the father?

In elegans, lon-2 and unc-2 are recessive mutations that are 8 map units apart on the X chromosome. An hermaphrodite who is Lon and Unc is mated to a wild-type male.  An F1 hermaphrodite is mated to a wild-type male.  What are the expected percentages of the different recombinant phenotypes among the male progeny?

What is chromosome theory of inheritence?

Given the karyotype shown at right, is this a male or a female? Normal or abnormal? What would the phenotype of this individual be?