Question

Nearly all microtubules in the cell originate from an organelle called centrosome which contains two centrioles. Which of the following statements is FALSE about centrosomes and centrioles?

	A.	Centrioles are essential for microtubule assembly both in vitro andin vivo.
	B.	The two centrioles in each centrosome are oriented perpendicularly to one other and each is formed by aligned microtubules.
	C.	Centrosomes are duplicated at the beginning of mitosis and each one of the two replicates is inherited by a daughter cells.
	D.	Centromeres contain centrioles, gamma-globulin rings and many other proteins.

Answer 1

Answer: D. Centromeres contain centrioles, gamma-globulin rings and many other proteins

Explanation:

Centromeres are actually specialized condensed region on each chromosome. It appears during mitosis and is the pint where the sister-chromatids are held together. It is an entity completely different from centrioles. Hence it is false that centromeres contain centrioles, etc.

Option A is true because the spindle network made of microtubules originates from centrioles

Option B is true because each centrosome has two centrioles which are at right angles to each other

Option C is true because the centrosomes get duplicated during the S-phase of cell cycle before mitosis

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