Karyotype

A karyotype is an organized visual representation of the chromosomes of a single cell. It is typically created by staining chromosomes during metaphase or prometaphase of cell division, when they are most condensed and visible. These stained chromosomes are then photographed under a microscope, cut out of the photograph (or digitally manipulated in modern techniques), and arranged in pairs based on size, banding patterns, and centromere position.

The purpose of creating a karyotype is to analyze the chromosome complement of an individual. This allows for the detection of chromosomal abnormalities, such as aneuploidy (an abnormal number of chromosomes, e.g., trisomy 21 in Down syndrome), deletions, duplications, inversions, and translocations. Karyotyping is a valuable tool in genetics and clinical medicine for diagnosing genetic disorders, understanding the causes of infertility and recurrent miscarriages, and identifying chromosomal aberrations in cancer cells.

Human karyotypes normally consist of 46 chromosomes, arranged in 23 pairs. These include 22 pairs of autosomes (non-sex chromosomes), numbered from 1 to 22 based on decreasing size, and one pair of sex chromosomes (XX in females and XY in males). The sex chromosomes determine an individual's sex.

The analysis of a karyotype is typically performed by a trained cytogeneticist. They examine the chromosomes for any structural or numerical abnormalities and provide a report describing the findings. These findings can then be used to inform diagnosis, prognosis, and treatment decisions. High-resolution karyotyping can detect smaller chromosomal abnormalities than standard karyotyping techniques.