S phase: cell continues growing, starts duplicating DNA. Interphase itself is split into three stages, as follows: If a cell is not in interphase, it is undergoing mitosis (which is sometimes referred to as “M phase”). If you throw a prepared slide of cells under a microscope, chances are the majority of them will be sitting in interphase, looking relatively inactive and uninteresting. Not necessarily a true “phase” of mitosis, interphase is the normal, non-division state of somatic cells. Take a look at how each of these phases breaks down. Note: you will not need to know the names of these phases for the AP® Biology exam, but you will still be required to describe the steps. A fifth “phase,” known as interphase, is the state in which a somatic cell spends most of its lifespan. The process of cellular mitosis occurs in four primary phases: prophase, metaphase, anaphase and telophase. Mitosis The diagram shows Mitosis and celldivision as a cyclic process. Now that we’ve reviewed the necessary AP® Bio background, let’s get to the meat of this section: the actual processes of mitosis and meiosis. When gametes combine during sexual reproduction, the sets of chromosomes from both parents provide the chromosome pairs for future diploid cells. In humans, egg and sperm cells contain only 23 chromosomes. Reproductive gametes, on the other hand, are haploid cells, containing only one set of chromosomes. Human cells, for example, have 23 chromosome pairs (46 total chromosomes), with one set of genetic information inherited from each of that human’s parents. Non-reproductive somatic cells are diploid cells, containing two sets of chromosomes. As the names imply, a diploid cell contains two sets of genetic information in homologous chromosome pairs, while a haploid cell contains only one set of genetic information in single copies of each chromosome. Haploid CellsĬells come in essentially two “flavors”: diploid and haploid. In its most complete form, two identical “sister chromatids” are joined together by a centromere to form a full chromosome. Chromatids are formed from condensed chromatin and serve as one-half of each chromosome. Chromatin is its loosest, least-organized form, which usually floats freely around inside the defined envelope of the nucleus. These are essentially the three forms of a cell’s genetic material. Throughout our discussion of mitosis and meiosis, we will be talking only about eukaryotes.īefore we get into the specifics of each process, let’s go over some AP® Biology background information that will help us understand the differences between them. Keep in mind: prokaryotic cells do not have membrane-bound organelles like nuclei, and therefore do not undergo mitosis and meiosis as eukaryotic cells do (instead, they undergo binary fission). Mitosis is the method by which somatic (or non-reproductive) are created, while meiosisis the method that creates gametes (reproductive cells like sperm and eggs). The processes by which these new cells are developed are known as mitosis and meiosis. As a eukaryotic organism grows, its cells are constantly dividing and creating new cells according to the “genetic blueprint” of its DNA.
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