Mitosis

This page features a series of photographs of whitefish blastula cells in the various stages of mitosis.

Whitefish Blastula Cells in Interphase and Mitosis

Interphase
This cell is shown, as this is how all cells look before mitosis. Please be aware that Interphase is a phase of the cell cycle, but NOT a stage of mitosis.

Early Prophase Mitosis - Early Prophase
To begin mitosis, the nuclear membrane breaks down, while the chromosomes shorten and thicken (here, a chromosome is two chromatids, bound at a point called the centromere, making an "X" shape). The other structures important for mitosis are also forming (i.e. the centrioles).

Metaphase Mitosis - Metaphase
The mitotic spindle apparatus has now formed and lies on the poles of the nucleus (but remember, the nuclear membrane has broken down, so there is no distinctly delineated nucleus). The chromosomes are lined up along the cell's equator, also known as the equatorial plate, and are attached to the mitotic spindle apparatus via microtubules (to try and visualize the microtubules extending from the poles to the chromosomes on the equator, think of the Earth - it's as if rope was extending from the chilly north and south poles to the chromosomes basking in the sun at the equator). Here's the confusing part - When the individual chromatids (½ of the "X") are separated from the chromosome (the "X"), they are now each referred to as a chromosome (i.e. In metaphase, the chromosome, composed of two chromatids, separates into the individual chromatids, which are then renamed chromosomes, even though they were only one half of a chromosome only moments before!) - Whew!

Anaphase Mitosis - Anaphase
The newly formed chromosomes (which were recently chromatids while they were still ½ of the "X") are pulled along the microtubules toward opposite poles of the cell (like Monarch butterflies migrating back to Canada and the southern tip of South America (toward the poles) from Mexico (near the equator).

Telophase
Mitosis - Telophase
The chromosome have finished their migration to the poles and the mitotic structures breakdown. The plasma membrane of the cell pinches down along the equator creating two separate cells (similar to twisting a long balloon and forcing it to pinch in the middle). At this time, the chromosomes become indistinct (as they are during Interphase), the nuclear membrane forms again and the nucleolus reappears.

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Special thanks to Hans Christoffersen for the preparation of this page.

Send comments to:
Sandra K. Ackerley (ackerley@uoguelph.ca),
Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.

Latest page update: December, 2007.

Whitefish Blastula Cells in Interphase and Mitosis
		Interphase This cell is shown, as this is how all cells look before mitosis. Please be aware that Interphase is a phase of the cell cycle, but NOT a stage of mitosis.
		Mitosis - Early Prophase To begin mitosis, the nuclear membrane breaks down, while the chromosomes shorten and thicken (here, a chromosome is two chromatids, bound at a point called the centromere, making an "X" shape). The other structures important for mitosis are also forming (i.e. the centrioles).
		Mitosis - Metaphase The mitotic spindle apparatus has now formed and lies on the poles of the nucleus (but remember, the nuclear membrane has broken down, so there is no distinctly delineated nucleus). The chromosomes are lined up along the cell's equator, also known as the equatorial plate, and are attached to the mitotic spindle apparatus via microtubules (to try and visualize the microtubules extending from the poles to the chromosomes on the equator, think of the Earth - it's as if rope was extending from the chilly north and south poles to the chromosomes basking in the sun at the equator). Here's the confusing part - When the individual chromatids (½ of the "X") are separated from the chromosome (the "X"), they are now each referred to as a chromosome (i.e. In metaphase, the chromosome, composed of two chromatids, separates into the individual chromatids, which are then renamed chromosomes, even though they were only one half of a chromosome only moments before!) - Whew!
		Mitosis - Anaphase The newly formed chromosomes (which were recently chromatids while they were still ½ of the "X") are pulled along the microtubules toward opposite poles of the cell (like Monarch butterflies migrating back to Canada and the southern tip of South America (toward the poles) from Mexico (near the equator).
		Mitosis - Telophase The chromosome have finished their migration to the poles and the mitotic structures breakdown. The plasma membrane of the cell pinches down along the equator creating two separate cells (similar to twisting a long balloon and forcing it to pinch in the middle). At this time, the chromosomes become indistinct (as they are during Interphase), the nuclear membrane forms again and the nucleolus reappears.