Q.29 Which of the following is not a type of microtubule associated with mitotic spindle?
- Polar
- Astral
- Central
- Kinetochore
Central is not a type of microtubule associated with the mitotic spindle.
The mitotic spindle contains three main types of microtubules: astral, polar (or interpolar), and kinetochore. Each plays a distinct role in chromosome segregation during cell division.
Option Breakdown
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Polar microtubules: These extend between the two spindle poles, often overlapping at the midzone to establish bipolarity and aid chromosome congression.
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Astral microtubules: These radiate from centrosomes to the cell cortex, positioning the spindle and orienting it within the cell.
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Central microtubules: No such category exists; “central” may confuse with the central spindle (anaphase structure of interpolar microtubules), but it is not a standard type.
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Kinetochore microtubules: These form k-fibers attaching kinetochores to poles, pulling chromosomes apart in anaphase.
The mitotic spindle is a dynamic microtubule-based structure crucial for accurate chromosome segregation during cell division, and understanding its microtubule types in mitotic spindle—polar, astral, and kinetochore—is key for life sciences students.
Types of Microtubules in Mitotic Spindle
Microtubules in the mitotic spindle fall into three primary categories, each with unique origins, organizations, and functions.
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Astral microtubules emanate from centrosomes to the cell cortex, anchoring and positioning the spindle.
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Polar microtubules (also called interpolar) span between poles, overlapping centrally to maintain spindle shape and drive chromosome alignment.
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Kinetochore microtubules bundle into k-fibers, linking chromosome kinetochores to poles for segregation.
Central microtubules do not exist as a recognized type; the term might refer to the central spindle’s overlapping interpolar arrays in anaphase, but it is not classified separately.
Microtubule Type Origin Function Attaches to Kinetochores? Astral Centrosome Spindle positioning No Polar/Interpolar Centrosome Bipolarity, congression No Kinetochore Centrosome Chromosome segregation Yes Central N/A Not a type N/A Why Central is the Answer
In exam questions like “Which of the following is not a type of microtubule associated with mitotic spindle?”, Central stands out because standard biology texts list only astral, polar/interpolar, and kinetochore microtubules. This distinction helps in mastering cell biology for competitive exams.
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