B6A-3_CellCycles.ppt.pdf - Cell Cycles Life Cycles Cell Cycles Sex Ploidy 1.  DNA is the molecule of inheritance 2.  A chromosome is one long dsDNA

B6A-3_CellCycles.ppt.pdf - Cell Cycles Life Cycles Cell...

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Cell Cycles & Life Cycles Heyer 1 Cell Cycles, Sex, & Ploidy 1. DNA is the molecule of inheritance. 2. A chromosome is one long dsDNA. In eukaryotes, the dsDNA molecule is wrapped with histones & other proteins to form chromatin . 3. A gene (a discrete unit of heredity) is a specific region of DNA on a chromosome. Specific gene: instructions for a specific protein 4. Each chromosome = 100s–1000s of genes. Growth & Development – New cells produced – Need the right number of cells in the right location Either too few or too many is bad. Cell Replacement – Lost or damaged cells replaced Asexual Reproduction – New organism formed Sea star regenerating Cells divide to reproduce I. Asexual Reproduction offspring from single parent (daughter cells have identical DNA as parent cell) II. Sexual Reproduction offspring from union of egg and sperm (combine some DNA from both parent cells) Sperm cells and egg cell Budding Hydra Prokaryotes Divide Asexually Binary Fission “to split in half” A Chromosome (1 DNA molecule) is duplicated, separates, and then cell divides Binary fission of a bacterium
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Cell Cycles & Life Cycles Heyer 2 Eukaryotic Cells Have Multiple Chromosomes Eukaryotic cells have 5–20x more DNA per cell than do bacteria. Divided into linear dsDNA + histone & other proteins : chromosomes If straight, t ypical chromosome would be ~ 4 cm long. Humans have 46 different chromosomes So collectively amounts to ~ 2 m long dsDNA packed into each cell nucleus! (4 m after replication!) Eukaryotic Cells Have Multiple Chromosomes In division, each new cell needs the correct number and kind of chromosomes –Replicate and divide chromosomes in nucleus –Distribution of organelles Chromosomes Must Duplicate Before Division Human duplicated chromosome Chromosome duplication and separation [Semiconservative Replication] The Cell Cycle Ordered sequence of events in a cell ʼ s life Interphase (G 1 /S/G 2 ) : 90% of cell cycle – Most cellular activity Mitotic phase (M) – Mitosis = nucleus divides – Cytokinesis = cytoplasm & plasma membrane divides The eukaryotic cell cycle The Cell Cycle Interphase : 1. G 1 : G rowth stage, part 1 Cell is metabolically active and grows larger 2. S: S ynthesis stage DNA is replicated 3. G 2 : G rowth stage, part 2 More metabolism & growth The eukaryotic cell cycle All cell reproduction requires DNA duplication Each cell must have its own copy of genetic material DNA replication in S Stage of Interphase Then DNA must be separated ( segregation ) so that each cell has a complete copy Mitosis of Mitotic Phase
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Cell Cycles & Life Cycles Heyer 3 Duplicated chromosomes Duplicated chromosome: two sister chromatids Sister chromatids contain identical DNA Sister chromatids are held together by the centromere One chromatid Sister chromatid Centromere Early mitotic phase: chromatin condenses into distinct chromosomes chromatin condenses into distinct chromosomes Chromatin Chromosomes Mitosis
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