Several common chromosomal abnormalities are listed in the table below. A common type of aneuploidy is trisomy, which is when there are 3 copies of a particular chromosome instead of 2. The term given for having an incorrect number of chromosomes is aneuploidy. Should nondisjunction occur during meiosis, the resulting egg or sperm cell will have an incorrect number of chromosomes if this sex cell is then fertilized, the fetus will have a chromosomal abnormality. This occurrence is known as nondisjunction, and it is often triggered by a lapse during a mitotic checkpoint. Mitosis and cytokinesis can be viewed under a microscope.Įxercise 4: Nondisjunction Events During Meiosisįailure of chromosomes to separate during mitosis or meiosis will result in an incorrect number of chromosomes in daughter cells. This division of the cytoplasm is called cytokinesis. As mitosis is nearing its end and the cell is in telophase, the cytoplasm also divides so that both new cells will have their own fluid, organelles, etc. The spindle fibers, which are formed by the cell as mitosis progresses, are used to attach to chromosomes, align them down the middle of the cell, and pull chromosomes apart into their identical individual chromatids which will end up in separate cells.

Mitosis has several steps: prophase, prometaphase, metaphase, anaphase, and telophase ( Figure 2). Each copy will end up in its own cell at the end of M phase. In mitosis, DNA which has been copied in the S phase of interphase is separated into two individual copies. Mitosis is the division of the nucleus and its contents. M phase, which consists of mitosis and cytokinesis, is the portion of the cell cycle where the cell divides, reproducing itself. The replication of a cell is part of the overall cell cycle ( Figure 1) which is composed of interphase and M phase (mitotic phase). All cells come from preexisting cells and eukaryotic cells must undergo mitosis in order to form new cells.

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