Lecture10Notes - Roles for mitotic cell replication Asexual...

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1 Mitosis and Cell Cycle Principles of Biology Lecture 9 Prof. David Fitch Roles for mitotic cell replication Asexual reproduction – e.g., single-celled organisms – e.g., multicellular plants from cuttings Development of multicellular organisms from zygote – e.g., ~2 x 10 14 (200 trillion) cells in an adult human Renewal and repair – e.g., new red blood cells Cell division stats Human development – 1 zygote becomes ~10 14 cells – What is the minimum number of division rounds? Red blood cell division rates – RBC lives 120 days – Average adult human has 5 L blood – Each µ L of blood has 5 million RBCs How many new cells are produced each second to replace the entire RBC population? Features of mitosis Replication of DNA Chromosomes are packed – Human cell has 2m DNA (250,000 x cell diameter) Diploid cells have 2 sets of genomes (2n) – Human somatic cells have 23 pairs of "homologs"; 2n=46 Replication leads to "sister chromatids"… Features of mitosis: replicated chromosome 0.5 µ m Chromosome duplication (including DNA synthesis) Centromere Separation of sister chromatids Sister chromatids Centrometers Sister chromatids A eukaryotic cel has multiple chromosomes, one of which is represented here. Before duplication, each chromosome has a single DNA molecule. Once duplicated, a chromosome consists of two sister chromatids connected at the centromere. Each chromatid contains a copy of the DNA molecule. Mechanical processes separate the sister chromatids into two chromosomes and distribute them to two daughter cel s. Result of cell division: clones Replication Equal distribution of genetic material Diploidy Clones Cytokinesis Mitosis 2n 2n 2n Mother Cell Diploid Diploids 2n 2n Diploids 2n 2n Diploids Daughter Cells
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2 Mitosis vs. Meiosis Meiosis only in germ cells Result is haploid cells (1n) (to be encountered later…) 2n 1n 1n Mother Cell diploid (homologs segregate) 1n 1n haploids 1n 1n haploids Crossing-over & segregation Mitosis-like sep. of copies Chromosome nomenclature A chick has 78 (=2n) chromosomes per somatic cell.
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This note was uploaded on 11/03/2010 for the course BIOLOGY V23-0011-0 taught by Professor Fitch during the Fall '10 term at NYU.

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Lecture10Notes - Roles for mitotic cell replication Asexual...

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