1362-SU09-Lecture-1-_36706

1362-SU09-Lecture-1-_36706 - Omniscellula ecellula...

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“Omnis cellula e cellula” (“every cell from a cell” – Virchow, 1855) The ability to reproduce is a fundamental property of all life; this process is cell based and is referred to as cell division . Depending on the organism, cell division can have different roles: 100 μm 200 μm 20 μm (a) Reproduction; asexual (b) Growth & development from fertilized egg (c) Tissue renewal (Regeneration) Unicellular types: Prokaryotes & Multicellular Eukaryotes ese types of cell division yield daughter cells Eukaryotes These types of cell division yield daughter cells genetically equivalent to the parent cell; i.e., clones.
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Organization of Genetic Material l ivision volves the accurate replication and equal arti • Cell division involves the accurate replication and equal parti tioning of a cell’s DNA (genome) into two daughter cells. •Th i s is a relatively simple & rapid process for prokaryotes that possess a single, circular double helical DNA molecule, compared to… •… eukaryotes , whose DNA is packaged into multiple, linear chromosomes inside a nucleus. [a human cell’s genome >6 feet long!] [ g g] Chromosomes in a cell of a lily • Eukaryotic species possess a particular chromosome number in each cell nucleus. Somatic cells: 2 chromosome sets; diploid (2n) . Gametes :1 chromosome set; haploid (n) . l id di b t f h d Ploidy : describe sets of chromosomes possessed by a eukaryote; e.g., tetraploid (4n) karyotic chromosomes: Eukaryotic chromosomes: •E a c h is composed of DNA wound around specific proteins; this DNA:protein assemblage is called chromatin .
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Eukaryotic DNA •T h e massive amount of DNA (10 9 bp) in a eukaryote assumes a hromatin structure of a highly coiled configuration in order to fit in the nucleus. Chromatin structure of a chromosome is shown: In non dividing cells, or in cells replicating their DNA, chromosomes appear as thin chromatin filaments. degree of coiling increases Chromosomes assume a more highly condensed (compacted) form l l i DNA li ti i ti f ll di i i following DNA replication, in preparation for cell division. Condensation of chromosomes facilitates their movement during cell division. •D N A is compacted by coiling it around spherical proteins called histones; this assemblage (i.e., DNA & protein) is referred to as chromatin :
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Eukaryotic Chromosome Terminology ster chromatids 0.5 μm Chromosomes DNA molecules Sister chromatids are identical*; held together by di Chromosome duplication ncluding DNA Chromo some arm condensin proteins; most closely attached at (including DNA synthesis) Centromere ster the centromere . The process of itosis sults in Sister chromatids Separation of mitosis results in separation & segregation of sister chromatids Centromere sister chromatids & their movement to two new nuclei Sister chromatids forming in the cell.
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This note was uploaded on 04/23/2010 for the course BIOL 1361 taught by Professor Knapp during the Spring '05 term at University of Houston.

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1362-SU09-Lecture-1-_36706 - Omniscellula ecellula...

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