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The Cellular Basis of Inheritance: Chromosome Structure and Cell Cycle

This chapter explores the cellular basis of inheritance, including the processes of asexual and sexual reproduction, chromosome structure, and the cell cycle. It explains the different stages of mitosis and meiosis, and how genetic material is passed on to offspring.

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The Cellular Basis of Inheritance: Chromosome Structure and Cell Cycle

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  1. Chapter 9 The Cellular Basis of Inheritance

  2. Reproduction • Asexual – process in which a single cell or set of cells produces offspring that inherit all their genetic material from one parent • Ex. Binary fission – bacteria • Sexual – process in which genetic material from two parents combines and produces offspring that differ genetically from either parent • Fertilization – egg fuses with sperm (zygote) • Cellular division – division of the genetic material of a cell in which two new cells are created

  3. Chromosome Structure • Nucleus – control center of cell • Contains DNA • Chromatin – thin fibers of protein and DNA found in a non-dividing cell • Chromosomes – Condensed, coiled, chromatin, that forms in dividing cells • Chromatid (sister) – each half of a duplicated chromosome • Centromere – Site of attachment for chromatids

  4. Chromosome Structure

  5. Chromosome Numbers • Each species has a characteristic number of chromosomes • Humans – 46, 23 pairs • Fruit Flies – 8 • Chimps – 48 • Carrot - 18

  6. Chromosome Numbers • Humans • Sex Chromosomes (2) Determine the sex • Male XY • Female XX • Autosomal Chromosomes (44)

  7. Chromosome Numbers • Homologous Chromosomes – One of a pair of morphologically similar chromosomes (mother, father) • Carry genes for the same traits • Karyotype – a technique for examining the chromosome makeup of an individual

  8. Chromosome Numbers • Diploid (2N) • Cells that contains 2 of each type of chromosome • Somatic cells – body cells • Haploid (1N) • Cells that contain only 1 set of chromosomes • Germ cells – those that give rise to gametes

  9. Cell Cycle • Cell Cycle • Sequence of events from the production of a eukaryotic cell to the time the cell itself reproduces • Three Stages in the cell cycle • Interphase • Mitosis • Cytokinesis

  10. Cell Cycle • Interphase • Period of cell growth and development before cell division (90% cells life) • 3 Phases of Interphase • G1 – Time of cell growth • S – Cells DNA is copied (replicated) • G2 – Cell prepares for division

  11. Cell Cycle • Mitosis • Cell (nuclear) division in which the number of chromosomes is kept the same from parent cells to daughter cells • 2N parent cell creates 2 diploid daughter cells • 4 stages of Mitosis • Prophase • Metaphase • Anaphase • Telophase

  12. Cell Cycle • Mitosis • Prophase • 1. Each duplicated chromosome (consisting of two sister chromatids) condenses from thread-like form to rod-like form • 2. Nuclear envelope and nucleolus disappear • 3. Centrioles form and move to opposite ends of the cell and give rise to spindle fibers • Spindle – football shaped framework of microtubules

  13. Cell Cycle • Mitosis • Metaphase (midway between) • Spindle fibers (microtubules) attach to the centromeres of the chromosomes and align them in the center of the cell (spindle equator)

  14. Cell Cycle • Mitosis • Anaphase • Sister chromatids of each chromosome separate and move to opposite poles • Each chromatid is now its own “daughter” chromosome

  15. Cell Cycle • Mitosis • Telophase • 1. Chromosomes return to threadlike form • 2. Nuclear envelopes begin to reform and separate the 2 new sets of chromosomes • 3. Spindle fibers disassemble • 4. Nucleolus forms in each of the newly forming cells

  16. Cell Cycle • Cytokinesis • Division of the cytoplasm • Splitting of a parent cell into daughter cells • Plants • Cell plate – vesicles containing cell wall building substances fuse together and separate the two new cells • Animals • Cleavage furrow – area of cell membrane that pinches inward until 2 new cells are formed

  17. Mitosis Video Clip

  18. Meiosis The Formation of Gametes

  19. Meiosis • Meiosis • Cell (nuclear) division in which the chromosome number is cut in half • 2N cell divides to form 4 (1N) cells • Two cell divisions – 2 stages • Meiosis I • Prophase I, Metaphase I, Anaphase I, Telophase I • Meiosis II • Prophase II, Metaphase II, Anaphase II, Telophase II

  20. Meiosis • Prophase I • 1. Chromosomes condense to rod-like form • 2. Nucleolus and nuclear membrane disappear • 3. Centrosomes form and move to poles, give rise to spindle fibers • 4. Homologous chromosomes pair up creating a tetrad (4 chromatids) • Crossing over – part of chromatid may break off and attach to adjacent chromatid on the homologous chromosome • Genetic recombination – regrouping of genes due to an exchange of maternal and paternal genetic material

  21. Meiosis • Metaphase I • Spindle fibers attach to the centromeres, and homologous pairs line up side by side (tetrad) on the spindle equator

  22. Meiosis • Anaphase I • Homologous chromosomes are separated and moved to opposite poles

  23. Meiosis • Telophase I • Cytokinesis occurs and produces 2 haploid (1N) cells • Each new cell contains one chromosome from each homologous pair

  24. Meiosis • Prophase II • Spindle fibers form and attach themselves to the centromeres of the chromosomes

  25. Meiosis • Metaphase II • Chromosomes are moved to the equator of the cell

  26. Meiosis • Anaphase II • Chromatids separate and move toward opposite poles of the cell

  27. Meiosis • Telophase II • 4 daughter nuclei • Each cell has a haploid chromosome number and all are in the unduplicatedstate • Gametes (sperm, egg)

  28. Meiosis Video Clips pull up video on flash drive copy & paste address: http://highered.mheducation.com/sites/0072507470/student_view0/chapter28/animation__how_meiosis_works.html

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