During which stage of mitosis do spindle fibers attach to the centromeres of chromosomes?
A. Prophase
B. Prometaphase
C. Anaphase
D. Metaphase
Answer: Option B
Solution (By JKSSB Mock Tests)
In prometaphase, the nuclear envelope breaks down, and spindle microtubules attach to kinetochores at the centromeres of chromosomes. This is a crucial step before alignment. In prophase, chromosomes condense; metaphase aligns them at the equator; anaphase separates chromatids. Prometaphase follows prophase in many descriptions.
Consider the following statements about the carbon cycle:
1. Photosynthesis removes CO₂ from the atmosphere.
2. Respiration and combustion return CO₂ to the atmosphere.
3. Decomposition releases CO₂.
Which of the above is/are correct?
In plant anatomy, the 'Vascular cambium' is a lateral meristem responsible for secondary growth (increase in girth) in dicots and gymnosperms. It produces secondary xylem (wood) towards the:
Explanation:
The vascular cambium is a thin layer of meristematic cells located between the primary xylem and primary phloem in the vascular bundles of dicot stems and roots, and in the secondary vascular tissue. It is a lateral meristem that divides periclinally (parallel to the surface). It produces secondary xylem (wood) cells towards the inside (center) of the stem or root, and secondary phloem (inner bark) cells towards the outside (periphery). Since it produces xylem much faster than phloem, the secondary xylem accumulates and forms the bulk of the wood.
Explanation:
Rhodopsin (visual purple) in rod cells of the retina consists of opsin and retinal (derived from vitamin A). It bleaches in light, triggering nerve impulses. It is highly sensitive, enabling night vision. Iodopsin is in cones for color vision.
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