Polysomic refers to a cell or organism that has an abnormal chromosome number, specifically involving the presence of extra copies of one or more chromosomes, but not of the entire genome (i.e., not polyploidy). This chromosomal variation arises during meiosis or mitosis, leading to an uneven distribution of chromosomes in the daughter cells. The resulting imbalance in gene dosage can disrupt normal development and function, often causing specific phenotypic effects depending on which chromosomes are affected and the organism in question. The suffix "-somic" indicates the deviation in chromosomal number. The consequences can range from subtle to severe, impacting viability and the observable characteristics of the individual.
Polysomic meaning with examples
- A patient diagnosed with Klinefelter syndrome is described as being polysomic for the X chromosome, having an XXY genotype instead of the normal XY. This polysomic condition results in various physical and developmental traits, including reduced fertility and taller stature.
- In humans, trisomy 21, commonly known as Down syndrome, is a well-known example of a polysomic condition. Individuals with Down syndrome possess three copies of chromosome 21. This polysomy is associated with characteristic facial features, intellectual disability, and increased risk of certain health problems.
- Research on plant genetics may focus on the creation of new varieties with desirable traits using polysomic techniques, where extra copies of particular chromosomes contribute to enhanced characteristics like disease resistance or fruit size. This strategy focuses on using polysomy in desired variations.
- During cellular division, errors during chromosome segregation can lead to a polysomic gamete that when fertilized gives an embryo that is monosomic or trisomic for that chromosome. Such errors can result in miscarriage if the chromosomal imbalance is too severe, highlighting the need for genetic screening.