Review Questions: 1. What is meant by the following terms: Homologous chromosomes- A matched pair of chromosomes‚ one derived from each parent. Both members of the pair are similar in size‚ shape‚ and appearance‚ except for sex chromosomes. Autosomes- The general term for chromosomes other than the sex chromosomes. Sex chromosome- The X and Y chromosomes that determine genetic sex. Barr body- The inactivated X chromosome that appears as a small‚ dense mass of chromatin attached to the nuclear
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WHAT IS A CELL? It is the smallest unit of life that is classified as a living thing‚ and is often called the building block of life. The cell is the basic structural and functional unit of all known living organisms. Some organisms are unicellular (made of only one cell) while others are multicellular (made up of several cells). The word cell comes from the Latin cellula‚ meaning‚ a small room. The term was coined by Robert Hooke in a book he published in 1665 when he compared the cork cells he
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S‚ a cell replicates its chromosomes‚ new DNA molecules are produced‚ and a cell replicates it’s chromosomes. In the final stage of interphase‚ G2‚ a cell gets ready to divide and the organelles and molecules needed for cell division are produced. After interphase‚ the cell begins mitosis. The mitosis stage is made up of four smaller phases. The phases‚ in order‚ are prophase‚ metaphase‚ anaphase‚ and telophase. During prophase‚ the chromatin condense into chromosomes‚ the centrioles separate‚
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Mitosis or cellular replication Some Important Terms for Replication: Chromosome – rod-shaped body in the nucleus that is only visible during replication that contains DNA and is our hereditary unit. Nucleolus – organelle inside the nucleus composed of RNA for ribosome formation. Spindle – microtubule structure that brings about chromosome movement during cell division. Chromatids – two identical parts of a chromosome following DNA replication. Centromere – site where sister chromatids are
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Why do cells divide? There are many reasons for this. Cells absorb and release nutrients threw their membrane. The larger the cell‚ the harder it is to get rid of all the waste that is produced. So‚ if there are many small cells (more surface area) rather than one large cell‚ the waste can be disposed of more readily. The other 3 reasons are critical to the survival of all organisms: Growth‚ repair and reproduction. • Growth: This is a result of mitosis. The more cells in an organism‚ the larger
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interphase or interkinesis‚ varies greatly but is considerably longer. During INTERPHASE the chromosomes are dispersed in the nucleus and appear as a network of long‚ thin threads or filaments‚ called the chromatin. At some point before prophase begins‚ the chromosomes replicate themselves to form pairs of identical sister chromosomes‚ or chromatids; the deoxyribose nucleic acid (DNA) of the chromosomes is synthesized only during interphase‚ not while mitosis is in process. During PROPHASE the two
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of protein that lets the cell know how many times it has divided. 1. The cell duplicates its chromosomes so that it now has double as many‚ but they remain attached. 2/3. The cell begins to split until it has the chromosomes have separated completely‚ to form two separate set of chromosomes. The cell begins to divide. 4. The cell divides completely to form two diploids (cells with all 46 chromosomes). When It Goes Wrong Although errors in mitosis are rare‚ the process may go wrong‚ especially
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Mitosis * Next stage of cell cycle & usually the shortest. * Process in which contents of cell’s nucleus divides. * Division results in 2 daughter nu kinds of chromosomes as original cell. * As nucleus prepares to divide‚ DNA molecules that replicated during interphase join together to form sister chromatids of chromosome.
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same number and type of chromosomes as the parent cell and will be identical to each other. Although cell division is the defining characteristic of mitosis‚ a number of events must take place during mitosis prior to the splitting of the cell. There are four phases that constitute the period in which cells make preparation for cell division. The four phases are prophase‚ metaphase‚ anaphase and telophase. Prophase‚ the first stage of mitosis during which the chromosomes become shorter‚ thicker
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5. Identifiable chromosomes are present in the cell only during…. D) M 8.1.2 Mitosis: an overview 1. Which statement regarding chromosomes is FALSE? C) An acrocentric chromosome has its centromere on the end of the chromosome.
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