Question
Question: What is the difference between astral rays and spindle fibres?...
What is the difference between astral rays and spindle fibres?
Solution
Astral rays are one variant of the microtubule which comes out of the centrosome. Other examples of microtubules include kinetochore microtubules and polar microtubules. During prophase, two aster-covered centrosomes move to the opposite sides of the nucleus in preparation for mitotic spindle formation.
Complete answer:
In a properly formed mitotic spindle, bi-oriented chromosomes are aligned along the equator of the cell with spindle microtubules oriented almost perpendicular to the chromosomes, where their plus-ends embedded in kinetochores and their minus-ends are anchored at the cell poles.
Differences between astral rays and spindle fibres are listed below.
| Astral rays | Spindle fibres |
|---|---|
| Astral spindle rays are formed around the centrioles in the cell. | Spindle fibres arise from the pole towards the centre. It is a cellular bipolar fibrillar structure made by proteins, myosin and actin. |
| The fibres radiating from the centriole form a star-shaped structure. | They run in between the two daughter centrioles forming the shape of a spindle. |
| They are not attached to the chromosome. | They remain attached to the chromosome. |
| The microtubules separate the chromosomes to cell poles with the help of spindle fibres. | Microfilaments made from these proteins bind to the centromeres of chromosomes. |
The cellular spindle apparatus comprises the spindle microtubules, associated proteins, which include kinesin and dynein molecular motors, condensed chromosomes, and any centrosomes or asters that may be present at the spindle poles depending on the cell type.
Note: Acentrosomal or an astral spindles do not have centrosomes or asters at the spindle poles, respectively, and occur during female meiosis in most animals. Besides the chromosomes, the spindle apparatus is composed of hundreds of proteins. The spindle apparatus is referred to as the mitotic spindle during the process of mitosis, which is a process that produces genetically identical daughter cells, or the meiotic spindle during meiosis.