Question

At metaphase, chromosomes are attached to their spindle fibres by their
A. Satellites
B. Secondary constrictions
C. Kinetochores
D. Centromere

Answer 1

Metaphase is the third phase of the mitosis cell division in somatic cells where the chromosomes are lined up at the metaphase plate or the centre of the cell. It is the shortest phase of the mitotic cell cycle as it takes only four per cent of the total time.

Complete answer:
Mitosis, also called the equational division, is a part of a cell cycle where one cell divides into two identical daughter cells. These cells have the same number of chromosomes as the chromosomes are equally distributed. The various stages of Mitosis are- Prophase, Prometaphase, Metaphase, Anaphase, and Telophase.

Metaphase- the shortest phase of the mitotic cycle, is when all the chromosomes are visible under the microscope. The entire genetic material is condensed into chromosomes, and as a result, the nucleus disappears. All the chromosomes are captured by the spindle fibres and lined at the metaphase plate. These chromosomes are attached to the opposite spindle poles by the spindle fibres formed by the microtubules joining the kinetochores of each chromosome. These spindle fibres originate as microtubules or long protein filaments, from the centrioles positioned at the opposite poles during cell division. These spindle fibres pull the chromosomes towards the poles through the kinetochores resulting in the partition or division of cells.

Option C: Chromosomes are attached to the spindle fibres by their Kinetochores, a disc-shaped protein structure. Therefore, this is the correct option.
All the other options are irrelevant.

Hence, the correct answer is option (C)

Note: The metaphase phase has a checkpoint, also called Mitotic checkpoint or Spindle checkpoint or Metaphase to Anaphase checkpoint which ensures that all the chromosomes are attached to the spindle fibres by their kinetochores. This ensures that the chromosomes are equally divided into the two daughter cells.