Metaphase under microscope

Perhaps the most amazing thing about mitosis is its precision, a feature that has intrigued biologists since chromosome movements in living cells. Researchers now know that mitosis is a highly regulated process involving hundreds of different cellular proteins. The dynamic nature of mitosis is best appreciated when this process is In his pioneering studies of mitosis, Flemming noted that the nuclear material, which he named " chromatin" for its ability to take up stains, did not have the same appearance in all cells. (We still use the word "chromatin" today, albeit in a more biochemical sense to refer to complexes of nuclear DNA and protein.) Specifically, in some cells, chromatin appeared as an amorphous network, although in other cells, it appeared as threadlike bodies that Flemming named "mitosen." Based on his observations, Flemming had the insight to propose that chromatin could undergo reversible transformations in cells. Today, scientists know that Flemming had successfully distinguished chromosomes in the interphase portion of the cell cycle from chromosomes undergoing mitosis, or the portion of the cell cycle during which the nucleus divides (Figure 1). With very few exceptions, mitosis occupies a much smaller fraction of the cell cycle than interphase. The difference in DNA compaction between interphase and mitosis is dramatic. A precise estimate of the difference is not possible, but during interphase, chromatin may be hundreds or even thousands of times less co...

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In order to heal an injury, your body needs to replace damaged cells with healthy new ones...and mitosis plays a crucial role in this process! Mitosis is a process of cell division that helps you stay alive and healthy. In other words, in the world of cell biology, mitosis is kind of a big deal! But like with anything science-related, mitosis can be sort of confusing when you first try to understand it. The key idea is that the process of mitosis involves four phases , or steps, that you need to understand if you want to understand how mitosis works. In this article, we’re going to do the following things to break down the four steps of mitosis for you and help you get acquainted with the mitosis phases: • Briefly define mitosis and eukaryotic cells • Break down the four phases of mitosis, in order • Provide mitosis diagrams for the stages of mitosis • Give you five resources for learning more about the phases of mitosis Now, let’s dive in! Feature image: Jpablo cadand Juliana Osorio/ (Marek Kultys/ What Is Mitosis? Mitosis is a process that occurs during the The role of mitosis in the cell cycle is to replicate the genetic material in an existing cell—known as the “parent cell”—and distribute that genetic material to two new cells, known as “daughter cells.” In order to pass its genetic material to the two new daughter cells, a parent cell must undergo cell division, or mitosis. Mitosis results in two new nuclei—which contain DNA—that eventually become two identical cells...

To put that another way, meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes. In humans, the haploid cells made in meiosis are sperm and eggs. When a sperm and an egg join in fertilization, the two haploid sets of chromosomes form a complete diploid set: a new genome. In many ways, meiosis is a lot like mitosis. The cell goes through similar stages and uses similar strategies to organize and separate chromosomes. In meiosis, however, the cell has a more complex task. It still needs to separate sister chromatids (the two halves of a duplicated chromosome), as in mitosis. But it must also separate homologous chromosomes, the similar but nonidentical chromosome pairs an organism receives from its two parents. For instance, in the image below, the letters A, B, and C represent genes found at particular spots on the chromosome, with capital and lowercase letters for different forms, or alleles, of each gene. The DNA is broken at the same spot on each homologue—here, between genes B and C—and reconnected in a criss-cross pattern so that the homologues exchange part of their DNA. Image of crossing over. Two homologous chromosomes carry different versions of three genes. One has the A, B, and C versions, while the other has the a, b, and c versions. A crossover event in which two chromatids—one from each homologue—exchange fragments swaps the C and c genes. Now, each homol...