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Mitosis and meiosis

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BIOL 2030

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Jan 8th (lecture 2) Mitosis and meiosis cellular reproduction Genes are located on chromosomes Segregation of genes from generations to generations follow the segregation of chromosomes Segregation: separation from genes from parent to offspring Chromosomes are organized linearly Diploid & haploid eukaryotic organisms Many eukaryotes have 2 copies of each type of chromosomes in their nuclei: they are diploid (2N) Some eukaryotes (e.g. yeast) are haploid (N) Each chromosome is unique Diploid organisms are produced by the fusion of 2 gametes (mature reproductive cells), 1 from female parent and 1 from male parent The gametes are haploid (N). The fusion produce a diploid zygote (2N) Fruit fly is diploid with 8 chromosomes - come in pairs Chromosomal organization of haploid and diploid organisms Left N = 3 Right 2N = 6 Simplified sexual reproductive cycles Meiosis: diploid to haploid Mitosis 2N to 2N - not losing genetic information Started with female and male parent. what sex is the offspring? Sex chromosomes and autosomes In many diploid animals and some diploid plants, one pair of chromosomes is represented differently in the 2 sexes: Sex chromosomes One sex has a matched pair (e.g. XX in human female) while the other sex has an unmatched pair (e.g. XY in human male) it only 1 sex chromosome Chromosomes other than the sex chromosomes are called autosomes In some organisms there is only 1 sex chromosome in the male and 2 in the female 22 pairs of autosomes and 1 sex chromosomes (2 x) Locus in chromosome (gene) that controls hair color for example - same gene controlling hair in homologous chromosome BUT different allele so both could code for different hair colors 1 chromosome - ends are telomere Centromere is constricted region in the chromosome - microtubules -- 1 chromosome Both 1 chromosome - same but duplicated Mitosis & the eukaryotic cell cycle Cellular reproduction is a cyclical process of growth and division: cell cycle Cell cycle includes 2 phases: Mitotic (division) phase (M) and interphase with 3 stages (G1, S and G2) Division phase comprises mitosis (nuclear division or karyokinesis) followed by cell division (cytokineses) Duplication of chromosomes takes place during the S stage (sister chromatid) Involves growth of the cell and division 2 phases: Division and an interphase (which has 3 stages) Division comprises mitosis - division of genetic material in nucleus S = synthesis G1 = cell prepares for the synthesis phase Checkpoint - when passed it is committed to the S phase - some cells never go into a mitotic cell division In the S phase - synthesis G2 = sub phase where the cell is preparing for the rest of the cycle Mitosis Prophase (developing spindle) Prometaphase (mitotic spindle) Metaphase (metaphase plate) Anaphase (disjunction of the sister chromatids) Telophase Cytokineses Interphase: chromosomes not visible Prophase: Chromosome condense (see them) centrosome migrate to opposite sides at the end you can see all the chromosomes and they are all duplicated Prometaphase: Microtubule moves into area and attach to each chromosome at the centromere Metaphase: aligning of the chromosome - on the metaphase plate - half way in the cell.
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