Chromosomes are classified as metacentric, sub-metacentric, acrocentric and telocentric. This classification is based on the position of which one of the following structures?
Show Hint
Remember that "centro-..." terms can be confusing.
Associate "centromere" directly with the chromosome structure ("mere" means part/segment), while "centrosome" and "centriole" are microtubule-organizing centers in the cytoplasm.
Step 1 : Understanding the Question:
The question asks to identify the organelle or chromosomal structure whose physical position determines the classification of chromosomes into metacentric, sub-metacentric, acrocentric, and telocentric types. Step 2 : Key Formulas and Approach:
The approach involves recalling the structural anatomy of a eukaryotic chromosome and understanding how the position of the primary constriction (centromere) divides the chromosome arms. Step 3 : Detailed Explanation:
• Centromere: The centromere, or primary constriction, is the region of the chromosome where sister chromatids are held together and spindle fibers attach during cell division.
• Metacentric: The centromere is located in the middle, dividing the chromosome into two equal arms.
• Sub-metacentric: The centromere is situated slightly away from the middle, resulting in one slightly shorter arm and one longer arm.
• Acrocentric: The centromere is positioned close to one end, producing one extremely short arm and one very long arm.
• Telocentric: The centromere is located at the terminal end, so the chromosome has only one visible arm.
• Other structures like the centrosome and centriole are involved in spindle formation but are not part of the chromosome itself, while the telomere represents the protective end caps of the chromosome. Step 4 : Final Answer:
Therefore, the classification is based on the position of the centromere.
This matches Option (A).
