Nursing Entrance Exam

Mitosis Cell Division During mitosis the cell divides its nucleus and then separates its organelles and chromosomes into two identical parts. The mother cell then divides into two genetically identical cells with equal parts of the cellular contents. The nuclei, cell membrane, organelles and cytoplasm of the cell would be shared between the two new cells. Mitosis cell division is complex and fast. The process takes place in stages, with each stage comprising of a set of activities that lead to the next stage. The stages of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis occurs in some unicellular organisms and within animal and human cells. Unicellular organisms use mitosis to reproduce, and within animal and humans, mitosis is used to replace cells and repair tissues. Meiosis Meiosis occurs when one cell from the male and one from the female combine or fuse to form one diploid cell, which then splits to form four haploid cells. The diploid cell contains copies of the chromosome and genetic information from both parents. The resulting four haploid cells will contain a copy of each chromosome. Each chromosome in the four cells will contain a unique blend of the paternal and maternal genetic information, which makes it possible for the offspring to share some genetic resemblance to both parents while remaining genetically distinct from both of them. This nature of meiosis cell division is what accounts for the genetic diversity that is available today, as each offspring’s DNA is a unique blend of its maternal and paternal genetic DNA. Mitosis and meiosis have some similarities in that they are both types of cell division among living organisms. However, there are still some differences between them. For example, mitosis occurs within a cell with no interactions with other cells. The individual cell simply divides and produces two genetically identical cells. With meiosis, the process involves two cells from both the male and female in a form of sexual reproduction. The resulting four cells are are genetically different from their parents. The process of meiosis was discovered by Oscar Hertwig and mitosis was discovered by Walther Flemming. 9.2.3 Mendel’s Laws of Heredity Phenotypes and Genotypes The terms “phenotype” and “genotype” were first introduced in 1911 by Wilhelm Johannsen. Genotype refers to the genes of an organism that contains its complete hereditary information. Phenotype refers to the actual observed properties of the organism – morphology, behavior, and

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