Final answer:
Chromosomes are matched in a karyotype using visually observable characteristics such as size and centromere position, which are readily identified when chromosomes are stained and examined under a microscope. Homologous chromosomes, recognized by their identical length and gene locations, are arranged from largest to smallest with distinct banding patterns.
Step-by-step explanation:
To match chromosomes in a karyotype, geneticists typically use characteristics such as size and centromere position. These features are visually apparent and can be observed when the chromosomes are stained and viewed under a microscope. The matched pairs of chromosomes, known as homologous chromosomes, are the same length and have genes at identical loci, which is crucial for identifying corresponding chromosomes in a diploid organism.
Moreover, the chromosomes can be arranged by size, from the largest autosomes to the smallest, which in a human karyotype would be chromosomes 1 through 22, followed by the sex chromosomes, X and Y. Centromere position is also key, as it divides each chromosome into a short arm (p) and a long arm (q). These provide further identifiable features, as the arms will have specific lengths and banding patterns unique to each chromosome that facilitate the matching process.
It is important to note, however, that although characteristics like number of genes or DNA sequence are integral to chromosomal functions, they are not typically used for visually matching chromosomes because they require more complex analysis that is not as readily performed through karyotyping. Similarly, histone content is not a visual characteristic used for this purpose.