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Reproduction of Cells

Reproduction of Cells . The Processes of Cell Division --- Mitosis and Meiosis. Cell Size Review…. What are some of the difficulties a cell faces as it increases in size?. Cell Size Review….

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Reproduction of Cells

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  1. Reproduction of Cells The Processes of Cell Division --- Mitosis and Meiosis

  2. Cell Size Review… What are some of the difficulties a cell faces as it increases in size?

  3. Cell Size Review… • The larger a cell becomes, the more demands the cell places on its DNA. In addition, a larger cell is less efficient in moving nutrients and waste materials across its cell membrane.

  4. Cell Size and Limits • Living cells store critical information in DNA. • As a cell grows, that information is used to build the molecules needed for cell growth.

  5. Cell Division In order for cells to survive, they must constantly exchange ions, gases, nutrients, and wastes with their environment. These exchanges take place at the cell’s surface. To perform this function efficiently, there must be an adequate ratio between the cell’s volume and its surface area. As a cell’s volume increases, its surface area increases, but at a decreased rate. If you continued to increase the cell’s volume, it would soon be unable to efficiently exchange materials and the cell would die.

  6. Compensation For Cell Size Limitations • Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division. • Before cell division, the cell copies all of its DNA.

  7. Reproduction of Cells Section 1 Chromosomes Section 2 Cell Division & Mitosis Section 3 Meiosis Online interactive tutorial for additional materials: http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html

  8. By the Time We Finish This Segment … Describethe structure of a chromosome. Identifythe differences in structure between prokaryotic chromosomes and eukaryotic chromosomes. Describe the events of cell division in prokaryotes. Comparethe numbers of chromosomes in different species. Explainthe differences between sex chromosomes and autosomes. Distinguishbetween diploid and haploid cells.

  9. Chromosomes - Made of DNA + Protein Eukaryotes • DNA wrapped around proteins called histones. • Chromosomes are linear strands Prokaryotes • Simpler in structure than eukaryotes. • Chromosomes are circular

  10. Structure of a Chromosome

  11. Basic Terms • Chromosomes-the double helix (double strand of 2 sugar-phosphate backbones) and are tightly coiled up. • Chromatid- Pairing with another chromosome to form two sister chromatids. • Centromere – “button” that holds chromosomes together. • Chromatin (DNA+histones) - is the loose form of chromosomes seen during interphase.

  12. Anatomy of a Chromosome

  13. Chromatin - Interphase

  14. Rate of Cell Division – Which takes less time?? Prokaryotes Binary Fission - the process of cell division in prokaryotes. Eukaryotes Mitosis - nuclear division producing two identical daughter cells

  15. What is the difference between binary fission and mitosis? Binary fission … • Is a form of asexual reproduction of an organism (single-celled) Mitosis … • Is NOT a form of asexual reproduction • IS a form of cellular reproduction that produces new cells for growth, repair, and the general replacement of older cells

  16. Chromosome Numbers Each species has a characteristic number of chromosomes in each cell.

  17. Chromosome Numbers, continued Autosomes and Sex Chromosomes • Chromosomes in an organism that are responsible for making body cells = autosomes.(2n) = diploid • Skin, Muscle, Hair, Kidney, Blood, etc. • Sex chromosomesare chromosomes that determine the sex of an organism. (1n) = haploid • Humans have 23 PAIRS chromosomes, but 46 total chromosomes

  18. Chromosome Numbers, continued Diploid and Haploid Cells • Cells having two sets of chromosomes are diploid(2n). (Also known as somatic cells) • Most all cells in our body • Haploidcells (1n) have only one set of chromosomes. (Also known as gametes) • Sex cells • 1 comes from momand1 comes from dad

  19. Karyotype Karyotype– an organized profile of one’s chromosomes.

  20. Mitosis (Cell division in eukaryotes) Cellular division that produces 2 identical cells Somatic cells

  21. By the Time We Finish This Segment … • Name the two parts of the cell that are equally divided during cell division in eukaryotes. • Summarize the events of interphase. • Describe the stages of mitosis. • Compare cytokinesis in animal cells with cytokinesis in plant cells. • Explain how cell division is controlled.

  22. Cell Division in Eukaryotes Cell Cycle • The cell cycleis the repeating set of events in the life of a cell. • The cell cycle includes cell division and interphase. • Cell division in eukaryotes includes nuclear division, called mitosis, and the division of cytoplasm, called cytokinesis. THESE ARE ALL KINDS OF CELLS (somatic, diploid) EXCEPT…Sex CELLS!!!

  23. Reminder …. Types Of Cells and How They Divide Somatic cells = All cells EXCEPT sex cells Hair, Skin, Liver, Blood, etc. Go through the process of MITOSIS Sex cells (gametes) = Go through the process of MEIOSIS!

  24. Cell Division– Trick to help remember… • IPrayMoreAtTheChurch • Interphase– loooonnnnggggIntermission = longest stage of (NOT CONSIDERED PART OF MITOSIS!!!!) • G1 (growth), S (synthesis), G2 (prep for ÷) • G0 – can occur after G1, exiting the cell cycle; as is

  25. Cell Divisionin Eukaryotes, continued Interphase • Interphase consists of growth (G1), DNA replication (S), and preparation for mitosis (G2)

  26. Somatic cell DivisionSomatic cells (body cells) divide for the purpose of growth, replacement, and repair of damage cells or tissues. Interphase:Preparation = DNA replicates, chemicals and organelle synthesis occurs. Mitosis: Nuclear division occurs (P, M, A, T) Cytokinesis: Division of the cytoplasm occurs, forming 2 genetically similar diploid cells

  27. Cell Division - Steps of Mitosis Back to: (I)PrayMoreAtTheChurch • Prophase – the beginning of the PROduction as DNA forms into rod-shaped chromosomes • Sidebar notes: the 2 copies of the chromatids have occurred (S phase), and remain connected to each other by the centromere • As the centromeres separate, spindle fibers (microtubules – cell organelles chapter) radiate from the centromeres) … What macromolecule makes microtubules????

  28. Cell Division– Steps of Mitosis Continuing…. IPrayMoreAtTheChurch • Metaphase–chromosomes line up in the Middle • Anaphase – pullAway from and go to either side of the cell • Telophase – chromosomes return to a less Tightly coiled chromatin state with nuclear envelops and a nucleolus around each of the new cells • AT THIS POINT, the nucleus has split into 2, BUT NOT the cell itself…. Yet.

  29. Stages of Mitosis Notice that when the chromosomes separate = single chromosomes

  30. Cell Division– Cytokinesis Continuing…. IPrayMoreAtTheChurch - Cytokinesis – Cell Splits in the Center, resulting in 2 – 2n (diploid – non-sex) cells

  31. Cell Division - Cytokinesis • During cytokinesis in animal cells, a cleavage furrowpinches in and eventually separates the dividing cell into two cells. • In plant cells, a cell plateseparates the dividing cell into two cells.

  32. Control of Cell Division • Cell division in eukaryotes is controlled by many proteins. • Control occurs at three main checkpoints. • G1 (growth), S (synthesis), G2 (prep for ÷)

  33. Control of Cell Division, continued When Control is Lost: Cancer • Proteins that regulate cell growth are controlled by genes • If mutations occur with the genes, protein function is affected, resulting in disruption of cell growth and division • This disruption = uncontrolled growth of cells = Cancer

  34. Control of Cell Division, continued When Control is Lost: Cancer • An individual’s propensity for developing cancer depends on many factors • Family genetics • Exposure of carcinogens = cancer-causing agents • Genetic mutations (mutagens) that can occur from exposure to carcinogens

  35. MEIOSIS (Cell division of sex cells) Gametes

  36. By the Time We Finish This Segment … • Comparethe end products of meiosis with those of mitosis. • Summarizethe events of meiosis I. • Explaincrossing-over and how it contributes to the production of unique individuals. • Summarizethe events of meiosis II. • Comparespermatogenesis and oogenesis. • Define sexual reproduction

  37. Formation of Haploid Cells(Sex cells) • Meiosis- a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. • Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis. Meiosis occurs ONLY with sex cells ---- All other cells are called somatic cells

  38. Formation of Haploid Cells(Sex cells) • In order to finish cell division of haploid cells with the correct number of chromosomes… (steps of mitosis x 2) • Meiosis I and Meiosis II must occur • Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I. • Results in DOUBLE the number of chromosomes needed for haploid cells to successfully exist and function in cell division. • Therefore, Meiosis II must occur to complete the process resulting in 4 HAPLOID cells

  39. Stages of Meiosis – Notice split = TETRADS (2 Pair of Chromosomes)

  40. Stages of Meiosis – Notice split = TETRADS (2 Pair of Chromosomes), continued

  41. Formation of Haploid Cells(Sex cells) • During Prophase I of Meiosis: • Crossing-over = when portions of homologous chromosomes (single strand of a pair of chromosomes) exchange genetic material, occurs during prophase I and results in genetic recombination. • A reshuffling of genes occurs making individuals unique!! • Genetically DIFFERENT cell results • AND the forming tetrads of chromosomes

  42. Formation of Haploid Cells(Sex cells) During Anaphase I of Meiosis Independent assortment the random separation of homologous chromosomes. • Results in genetic variation or mixing of genetic traits. This is what allows you to have your dad’s color hair and your mother’s texture of hair!! 

  43. Formation of Haploid Cells(Sex cells) Meiosis II • Is very similar to Meiosis I, EXCEPT Meiosis II does NOT go through interphase again…. • Instead, Meiosis II begins in prophase II and continues through “PrayMoreAtTheChurch” • Meiosis II includes: prophase II, metaphase II, anaphase II, and telophase II. • Four new haploid cells result.

  44. Meiotic Cell Division

  45. Development of Gametes • Spermatogenesisis the process by which sperm cells are produced. • Oogenesisis the process that produces mature egg cells.

  46. Meiosis in Male and Female Animals

  47. Sexual Reproduction • Sexual reproductionis the formation of offspring through meiosis and the union of a sperm and an egg. • Offspring produced by sexual reproduction are genetically different from the parents.

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