Final answer:
When an egg missing a chromosome is fertilized by a normal sperm, it results in monosomy, which typically causes severe developmental issues due to only having one copy of essential genes.
Step-by-step explanation:
If an egg that is missing a chromosome is fertilized by a normal sperm, the result is monosomy. In humans, a normal euploid set of chromosomes is 46, with 22 pairs of autosomes and one pair of sex chromosomes. Monosomy means that the organism has only one copy of a particular chromosome instead of the usual two. This often results in severe developmental issues because one copy of essential genes is not sufficient for normal development. One example of monosomy in humans is Turner Syndrome, where there is only one X chromosome.