Biology STAAR Practice Test 2026 - Free State of Texas Assessments of Academic Readiness Practice Questions and Study Guide

A karyotype is a visual representation of an individual's chromosomes, typically arranged and displayed by size and shape. The primary purpose of a karyotype is to analyze the number of chromosomes present in an organism's cells, which allows researchers and healthcare professionals to identify chromosomal abnormalities.

The correct choice emphasizes the karyotype's ability to reveal whether an individual has the normal diploid number of chromosomes (46 in humans) or if there are any anomalies, such as an extra chromosome (as seen in Down syndrome, which involves trisomy 21) or a missing chromosome (such as Turner syndrome).

While a karyotype does provide information on the size and shape of chromosomes, which relates to the option that discusses the shape and size of chromosomes, the main application of a karyotype is to confirm variations in chromosome number. The option regarding mutations in DNA or genetic variations does not specifically pertain to the karyotype's primary focus, which is chromosome count rather than detailed genetic analysis.