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Understanding Cell Reproduction: Nucleic Acids & Chromosomes

Learn about the role of nucleic acids, structure of chromosomes, and cell division processes in biology. Explore topics such as DNA packaging, chromosome numbers, and the cell cycle phases in detailed notes.

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Understanding Cell Reproduction: Nucleic Acids & Chromosomes

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  1. Biology IChapter 8 Cell Reproduction

  2. Do Now (in notes section) What does a nucleic acid do? Store genetic information Make proteins Control cellular activities What is a nucleotide? The monomers of nucleic acids What organelle is directly involved in cell division? Nucleus

  3. Chromosomes Chromosome-rod-shaped structures made of DNA and proteins. In order to fit within a cell, DNA becomes more compact by wrapping tightly around associated proteins. Histone -the proteins that DNA wraps around.

  4. Chromosome Parts Chromatids- halvesof a chromosome. Centromere- a protein disk that attaches two chromatids to each other in a chromosome. Chromatin-less tightly coiled DNA-protein complex.

  5. Figure 2: Different levels of DNA condensation. • Single DNA strand. • Chromatin strand (DNA with histones). • Condensed chromatin during interphase with centromere. • Condensed chromatin during prophase. (Two copies of the DNA molecule are now present) • Chromosome during metaphase.

  6. Prokaryotic Chromosomes Chromosomes in prokaryotes are simpler in structure than chromosomes in eukaryotes. Prokaryotic chromosomes consist of one circular DNA molecule.

  7. Chromosome Number Sex Chromosome-chromosomes that determine the sex of an organism Autosome-Chromosomes that are not involved in sex determination

  8. Chromosome Number The chromosomes in your body Exist in 23 pairs Include two sex chromosomes Include 44 autosomes.

  9. DoNow • How many PAIRS of chromosomes are in the human body? • 23 • How many PAIRS of sex chromosomes are in the human body? • 1 • How many PAIRS of autosomes are in the human body? • 22

  10. Chromosome Numbers HomologousChromosomes- two copies of each chromosome Karyotype -A picture of a cell’s chromosomes

  11. Haploid & Diploid DiploidCell Has two homologues of each chromosome Is designated by the symbol 2n All human cells except reproductive cells (egg & sperm). Humans have 22 pairs of homologous chromosomes.

  12. Haploid & Diploid Haploid Cell-contain only one set of chromosomes. Have half the number of chromosomes that are present in diploid cells. Egg & sperm cells Is designated by the symbol “n.” n+n=2n

  13. Do Now What would a karyotype look like if it was a haploid cell? It would only have one of each chromosome.

  14. Cell Division in Prokaryotes Binary fission-the process by which bacteria reproduce. In a bacterium, cell division takes place when the DNA is copied, a new cell membrane forms between the DNA copies, and the cell splits into two cells. Binary Fission

  15. Binary Fission

  16. Do Now (in notes section) The diploid number of chromosomes in a human skin cell is 46. How many chromosomes are in a human egg cell? 23 How many chromosomes are in the body cells of an organism that has a haploid number of 8? 16

  17. Do Now (True or False, if false, make statement true) Sex chromosomes include the X and Y chromosomes. True All the nonsex chromosomes are called autosomes. True Haploid cells have one chromosome. False They have one of every chromosome.

  18. Cell Cycle Cell Cycle-the sequence of events that occurs in a cell from one mitotic division to the next. 3 Phases: Interphase Mitosis Cytokinesis Cell Cycle

  19. INTERPHASE http://www.youtube.com/watch?v=lf9rcqifx34 G1 S(DNA synthesis) G2 Cytokinesis Mitosis MITOTICPHASE (M)

  20. Interphase The time between cell divisions The cell spends most of its life cycle in interphase

  21. Interphase G1-offspring cells grow to mature size S Phase-the cell’s DNA is copied (synthesized) G2- cell continues to grow in preparation for mitosis. G0-cells do not copy their DNA and do not prepare for cell division.

  22. Mitosis The division of the nucleus Mitosis

  23. Prophase The chromosomes condense and become visible The centrioles form and move toward opposite ends of the cell ("the poles") The mitotic spindle forms (from the centrioles in animal cells) The nuclear membrane dissolves Spindle fibers from each centriole attach to each sister chromatid at the kinetochore

  24. Metaphase The Centrioles complete their migration to the poles The chromosomes line up in the middle of the cell ("the equator")

  25. Anaphase The chromatids of each chromosome separate at the centromere and slowly move, centromere first, toward opposite poles of the dividing cell.

  26. Telophase After the chromosomes reach opposite ends of the cell, the spindle fibers disassemble, and the chromosomes return to a less tightly coiled chromatin state. A nuclear envelope forms around each set of chromosomes, and a nucleolus forms in each of the newly formed cells.

  27. Cytokinesis The chromosomes and cytoplasm are equally divided between 2 offspring cells. Cleavage Furrow-the area of the cell membrane that pinches in. Cytokinesis occurs in plant cells when a new cell wall forms. Cell Plate-the dividing midline of plant cells

  28. Cell Division Mitosis refers STRICTLY to the division of the nucleus. Cytokinesis refers STRICTLY to the division of the cytoplasm. Cell Division

  29. Cell Cycle Interphase G1 S G2 Mitotic Phase Prophase Metaphase Anaphase Telophase Cytokinesis Crash Course-Mitosis

  30. LM 250 INTERPHASE PROPHASE PROMETAPHASE Centrosomes(with centriole pairs) Fragmentsof nuclearenvelope Centrosome Early mitoticspindle Kinetochore Chromatin Nucleolus Centromere Chromosome, consistingot two sister chromatids Spindlemicrotubules Nuclearenvelope Plasmamembrane

  31. TELOPHASE AND CYTOKINESIS ANAPHASE METAPHASE Nucleolusforming Cleavagefurrow Metaphaseplate Daughterchromosomes Nuclearenvelopeforming Spindle

  32. Why do you do mitosis? • Grow • Replace damaged or worn out cells • Produce identical offspring

  33. Do Now A typical human cell contains 46 chromosomes. After mitosis and cytokinesis, each of the two new cells formed from the original cell has ___ chromosomes. Complete set of 46 chromosomes.

  34. Cancer Cancer cells do not respond normally to the body’s control mechanisms. Cancer occurs as a result of disorders in cell division. Cancer

  35. Benign Tumor-Abnormal cells remain at the original site Malignant tumors-invade other tissues. Metastasis-the spread of cancer cells via the circulatory system beyond their original site. Lymphvessels Tumor Bloodvessel Glandulartissue Cancer cells invadeneighboring tissue. Cancer cells spread throughlymph and blood vessels toother parts of the body. A tumor grows from asingle cancer cell. Figure 8.10

  36. Formation of Haploid Cells Gamete-haploid reproductive cells Egg & Sperm Contain 23 chromosomes each

  37. Meiosis Interphase Cells preparing to divide by meiosis undergo G1, S, & G2. The cell grows to a mature size and copies its DNA Meiosis

  38. Prophase I The chromosomes condense and become visible The centrioles form and move toward the poles The nuclear membrane begins to dissolve The homologs pair up, forming a tetrad Each tetrad is comprised of four chromotids - the two homologues, each with their sister chromatid

  39. Prophase I Homologous chromosomes will swap genetic material in a process known as crossingover. CrossingOver- A reciprocal exchange of corresponding segments of DNA Crossing over serves to increase genetic diversity by creating four unique chromatids

  40. Crossing Over

  41. Metaphase I Microtubules grow from the centrioles and attach to the centromeres The tetrads line up along the cell equator

  42. Anaphase I Each homologous chromosome (consisting of 2 chromatids attached by a centromere) moves to an opposite pole. Independent Assortment-random separation of the homologous chromosomes occurs.

  43. Telophase I & Cytokinesis The chromosomes reach the opposite ends of the cell and cytokinesis begins.

  44. Meiosis II Occurs in each cell formed during meiosis I and is NOT preceded by the copying of DNA. (interphase)

  45. Prophase II Spindle fibers form and begin to move the chromosomes toward the midline of the dividing cell.

  46. Metaphase II Chromosomes move toward the midline of the dividing cell, with each chromatid facing opposite poles.

  47. Anaphase II Chromatids separate and move toward opposite poles of the cell.

  48. Telophase II A nuclear membrane forms around the chromosomes in each other four cells.

  49. Cytokinesis II Results in four new cells, each of which contain half of the original cell’s number of chromosomes. Meiosis Square Dance Crash Course-Meiosis Amoeba Sisters

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