What are kinetochores?

• A. Protein complexes on the centromere that allows for cell division
• B. Regions of DNA that code for ribosomal RNA
• C. Enzymes that unwind DNA during replication
• D. Sites on the cell membrane for attachment

Answer: (B)

Kinetochores are protein complexes located at the centromere of each chromosome. Their job is to serve as attachment points for the spindle’s microtubules during cell division, so chromosomes can align on the metaphase plate and then be pulled apart to opposite poles in an organized way. This connection between the chromosome and the spindle is essential for accurate chromosome segregation.

This isn’t a DNA region that codes for ribosomal RNA, which would be a DNA sequence involved in making rRNA. It isn’t a DNA-unwinding enzyme like helicase, which helps open the DNA double helix during replication. And it isn’t a site on the cell membrane for attachment. Kinetochores are specifically the protein structures at the centromere that mediate spindle attachment during mitosis and meiosis.