Chromosomes in karyotypes are arranged and ordered by
Group of answer choices
centromere position.
width.
length.
gene density.
The correct answer and explanation is:
The correct answer is length.
Chromosomes in karyotypes are typically arranged and ordered based on their length, from the longest to the shortest. This method allows for a clear and standardized way to compare chromosomes and identify any abnormalities or structural variations, such as deletions, duplications, or translocations.
Karyotyping involves photographing the chromosomes during a phase of cell division, usually metaphase, when the chromosomes are fully condensed and visible. These images are then analyzed, and the chromosomes are arranged in pairs. For the ordering process, chromosomes are usually grouped into a set of homologous chromosomes, with each chromosome numbered according to its relative size.
The reason length is the primary criterion for sorting chromosomes is because it provides a simple and consistent metric. Other factors like centromere position, gene density, and width can vary significantly between chromosomes of the same length and thus don’t provide the same level of organization. While the centromere position (whether it’s metacentric, submetacentric, or acrocentric) does affect the appearance of the chromosome, it is not the main determinant for karyotyping order. Similarly, gene density varies across chromosomes and can even vary along the length of individual chromosomes, making it less useful for sorting.
Chromosome length serves as a reliable tool in medical genetics, particularly in diagnosing chromosomal abnormalities. For example, an extra chromosome 21, which is the hallmark of Down syndrome, can be readily identified in a karyotype due to the distinct length and structure of the chromosome.