NEET BIOLOGY

Detailed explanation-1: -The spindle fibers form during prophase. During metaphase of cell division, the spindle fibers radiate from the centrioles at the opposite poles. Some of them attach to the kinetochores of the chromosomes while others bind to the arms of the chromosomes, still others continue to grow.

Detailed explanation-2: -During prophase, the nuclear envelope and nucleolus are dissolved and the chromosomes condense. The centrioles and spindle fibers begin to form at opposite poles of the cell. Chromatid separation is not seen until anaphase.

Detailed explanation-3: -Spindle fibers function twice during meiosis. Their role again is to attach to chromosomal structures and pull them apart to opposite ends of the cell. During both meiosis’ prophases, the spindle fibers become visible and then extend from centrosomes and centrioles at opposite ends of the cell during both metaphases.

Detailed explanation-4: -The sister chromatids are pairs of identical copies of DNA joined at a point called the centromere. Then, a structure called the mitotic spindle begins to form. The mitotic spindle is made of long proteins called microtubules that begin forming at opposite ends of the cell.