obtains the same number of chromosomes and the same nuclear code as the original nucleus is call mitosis. Mitosis occurs in four phases. Interphase occurs between mitosis. Interphase: Cell contains easily seen nucleus and nucleolus- chromosomes appear as fine dots within nucleus Mitosis: 4 steps Prophase – cell nucleus enlarged –nucleolus no longer visible- chromosomes appear as short strands within nucleus. Metaphase – chromosomes long and thin strands – chromosomes lined up along cell center
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Prophase 1 of meiosis When prophase I occurs the chromosomal condensation enables the chromosomes to be looked at under the microscope. Then during late prophase I the homologous chromosomes laterally pair or usually side by side which is then known to be in synapsis this is when cross connections form from Breakage and re-joining between the chromatids which can occur between the pair homologous chromosomes which then lead to genetic combination between the strands which are there. Chiasma occurs
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allele that only has an effect on the phenotype when present in the homozygous state. * Co-dominant alleles- pairs of alleles that both affect the phenotype when present in a heterozygote. * Locus- the particular position on homologous chromosomes of a gene * Homozygous- having two identical alleles of a gene * Heterozygous-having two different alleles of a gene * Carrier- an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are
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differences between mitosis and meiosis. 2. describe and recognize the stages of mitosis under a microscope or on models. 3. know the events that occur during each stage of mitosis and meiosis. 4. define the boldface terms. Chromosomes:
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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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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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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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