What effect does non-disjunction typically have on an organism?

Non-disjunction refers to the failure of homologous chromosomes or sister chromatids to separate properly during cell division, specifically in meiosis or mitosis. This error leads to gametes or cells with an abnormal number of chromosomes, which can have significant consequences for an organism's development and health.

When non-disjunction occurs, the resulting gametes may contain an extra chromosome (trisomy) or be missing a chromosome (monosomy). If such gametes participate in fertilization, the zygote will have an incorrect chromosome number, which can cause a variety of genetic disorders. For instance, Down syndrome, a well-known genetic disorder, is caused by trisomy of chromosome 21 and results from non-disjunction during gamete formation. Other disorders, such as Turner syndrome and Klinefelter syndrome, also arise from non-disjunction events.

The underlying mechanism by which non-disjunction leads to these disorders is directly linked to the imbalance in gene dosage that affects gene expression, leading to the phenotypic features associated with these conditions. Therefore, the impact of non-disjunction on an organism manifests as genetic disorders, making this answer the most accurate in reflecting the consequences of this cellular error.