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October, 2006
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Cytokinesis: The process by which the Cytoplasm of a cell is divided.

Mitosis and Cytokinesis

JoVE 10762

In eukaryotic cells, the cell's cycle—the division cycle—is divided into distinct, coordinated cellular processes that include cell growth, DNA replication/chromosome duplication, chromosome distribution to daughter cells, and finally, cell division. The cell cycle is tightly regulated by its regulatory systems as well as extracellular signals that affect cell proliferation. The processes of the cell cycle occur over approximately 24 hours (in typical human cells) and in two major distinguishable stages. The first stage is DNA replication, during the S phase of interphase. The second stage is the mitotic (M) phase, which involves the separation of the duplicated chromosomes into two new nuclei (mitosis) and cytoplasmic division (cytokinesis). The two phases are separated by intervals (G1 and G2 gaps), during which the cell prepares for replication and division. Mitosis can be divided into five distinct stages—prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis, which begins during anaphase or telophase (depending on the cell), is part of the M phase, but not part of mitosis. As the cell enters mitosis, its replicated chromosomes begin to condense and become visible as threadlike structures with the aid of proteins known as condensins. The mitotic spindle apparatus b

 Core: Biology

Cell Division- Concept

JoVE 10571

Cell division is fundamental to all living organisms and required for growth and development. As an essential means of reproduction for all living things, cell division allows organisms to transfer their genetic material to their offspring. For a unicellular organism, cellular division generates a completely new organism. For multicellular organisms, cellular division produces new cells for…

 Lab Bio


JoVE 10761

The cell cycle occurs over approximately 24 hours (in a typical human cell) and in two distinct stages: interphase, which includes three phases of the cell cycle (G1, S, and G2), and mitosis (M). During interphase, which takes up about 95 percent of the duration of the eukaryotic cell cycle, cells grow and replicate their DNA in preparation for mitosis.

Following each period of mitosis and cytokinesis, eukaryotic cells enter interphase, during which they grow and replicate their DNA in preparation for the next mitotic division. During the G1 (gap 1) phase, cells grow continuously and prepare for DNA replication. During this phase, cells are metabolically active and copy essential organelles and biochemical molecules, such as proteins. In the subsequent S (synthesis) phase of interphase, cells duplicate their nuclear DNA, which remains packaged in semi-condensed chromatin. During the S phase, cells also duplicate the centrosome, a microtubule-organizing structure that forms the mitotic spindle apparatus. The mitotic spindle separates chromosomes during mitosis. In the G2 (gap 2) phase, which follows DNA synthesis, cells continue to grow and synthesize proteins and organelles to prepare for mitosis. In human cells, the G1 phase spans approximately 11 hours, the S phase takes about

 Core: Biology

What is the Cell Cycle?

JoVE 10757

The cell cycle refers to the sequence of events occurring throughout a typical cell’s life. In eukaryotic cells, the somatic cell cycle has two stages: interphase and the mitotic phase. During interphase, the cell grows, performs its basic metabolic functions, copies its DNA, and prepares for mitotic cell division. Then, during mitosis and cytokinesis, the cell divides its nuclear and cytoplasmic materials, respectively. This generates two daughter cells that are identical to the original parent cell. The cell cycle is essential for the growth of the organism, replacement of damaged cells, and regeneration of aged cells. Cancer is the result of uncontrolled cell division sparked by a gene mutation. There are three major checkpoints in the eukaryotic cell cycle. At each checkpoint, the progression to the next cell cycle stage can be halted until conditions are more favorable. The G1 checkpoint is the first of these, where a cell’s size, energy, nutrients, DNA quality, and other external factors are evaluated. If the cell is deemed inadequate, it does not continue to the S phase of interphase. The G2 checkpoint is the second checkpoint. Here, the cell ensures that all of the DNA has been replicated and is not damaged before entering mitosis. If any DNA damage is detected that cannot be repaired, the cell may undergo apoptosis, or

 Core: Biology

Live Cell Imaging of Mitosis

JoVE 5642

Mitosis is a form of cell division in which a cell’s genetic material is divided equally between two daughter cells. Mitosis can be broken down into six phases, during each of which the cell’s components, such as its chromosomes, show visually distinct characteristics. Advances in fluorescence live cell imaging have allowed scientists to study this process in…

 Cell Biology

An Introduction to Saccharomyces cerevisiae

JoVE 5081

Saccharomyces cerevisiae (commonly known as baker’s yeast) is a single-celled eukaryote that is frequently used in scientific research. S. cerevisiae is an attractive model organism due to the fact that its genome has been sequenced, its genetics are easily manipulated, and it is very easy to maintain in the lab. Because many yeast proteins are similar in sequence and function…

 Biology I

Meiosis II

JoVE 10768

Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 chromosomes—one from each homologous initial pair. Importantly, each chromosome in these cells is composed of two joined copies, and when these cells enter meiosis II, the goal is to separate such sister chromatids using the same microtubule-based network employed in other division processes. The result of meiosis II is two haploid cells, each containing only one copy of all 23 chromosomes. Depending on whether the process occurs in males or females, these cells may form eggs or sperm, which—when joined through the process of fertilization—may yield a new diploid individual. Although the goal of meiosis II is the same in both males and females—to produce haploid egg or sperm cells—there are some critical differences in this process between the sexes. For example, in a woman’s egg precursor cells, the meiotic spindle apparatus responsible for separating sister chromatids forms off to one side, near the periphery. This asymmetry allows for two cells of unequal sizes to be produced following meiosis II: a large egg, and a smaller polar body that dissolves. This division of cytoplasm ensures that the egg contains enough nutrients to support an embryo. The position of the meiotic spind

 Core: Biology

Binary Fission

JoVE 10759

Fission is the division of a single entity into two or more parts, which regenerate into separate entities that resemble the original. Organisms in the Archaea and Bacteria domains reproduce using binary fission, in which a parent cell splits into two parts that can each grow to the size of the original parent cell. This asexual method of reproduction produces cells that are all genetically identical. Though its speed varies among species, binary fission is generally rapid and can yield staggering growth. In the amount of time it takes bacterial cells to undergo binary fission, the number of cells in the bacterial culture doubles. Thus, this period is the doubling time. For example, Escherichia coli cells typically divide every 20 minutes. Bacterial growth, however, is limited by factors including nutrient and space availability. Thus, binary fission occurs at much lower rates in bacterial cultures that have encountered a growth-limiting factor (i.e., entered a stationary growth phase). In addition to organisms in the Archaea and Bacteria domains, some organelles in eukaryotic cells also reproduce via binary fission. Mitochondria, for example, divide by prokaryotic binary fission. This process requires the division of mitochondrial proteins and DNA.

 Core: Biology

Cell Division - Prep Student

JoVE 10626

Preparation of Onion Root Tips and Solutions
For the cell cycle experiment using root tips, first, leave an onion suspended over a beaker of water to grow roots for several days.
Then, clean the onion roots of any dirt or debris.
Next, in a 1.5 mL tube, dissolve 10 mcg of nocodazole per 1 mL of dimethyl sulfoxide solution, making 1 tube…

 Lab Bio
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