1 / 36

Replication / Cell Division Notes

Replication / Cell Division Notes. Chapter 10 and 11. Maurice Wilkins and Rosaline Franklin - 1952. Photographed DNA using x-rays (crystallography) Showed a wide, tightly coiled molecule with a helix shape. James Watson and Francis Crick - 1953.

pules
Download Presentation

Replication / Cell Division Notes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Replication / Cell Division Notes Chapter 10 and 11

  2. Maurice Wilkins and Rosaline Franklin - 1952 • Photographed DNA using x-rays (crystallography) • Showed a wide, tightly coiled molecule with a helix shape

  3. James Watson and Francis Crick - 1953 • Used Franklin’s DNA x-ray to determine structure of DNA • DNA’s shape • Double helix • 2 strands • Rungs (nitrogen bases)

  4. DNA

  5. DNA Structure • Shape – double helix • Location – chromosomes contain DNA • Found in nucleus of eukaryotic cells • Length – long • E. coli – 4,639,221 base pairs or 1.6mm long • 1 m of DNA in each Eukaryotic cell

  6. Nucleotides • Nucleotide consists of: • 5-carbon sugar – deoxyribose • Phosphate group • One of 4 nitrogen bases • Adenine • Thymine • Guanine • Cytosine

  7. Nitrogen Bases • Base pair rule • Adenine always pairs with thymine • A:T • Guanine always pairs with cytosine • G:C • Adenine and guanine are purines • Thymine and cytosine are pyrimidines • Bases are held together by hydrogen bonds (weak)

  8. DNA Structure

  9. DNA Replication • Process by which DNA is copied • DNA reproduces prior to cell division • Steps • DNA double helix unwinds and unzips • Enzymes break H2 bonds between bases, separating 2 strands • Each parent strand of DNA serves as a template for each new strand • New strands are assembled from free nucleotides • DNA polymerase matches the bases on parent strand creating new double helixes

  10. Replication

  11. Why Cells Divide • Cell size • Maintain large surface area to volume ratios to transport materials easily • Minimum • DNA • Protein • Internal structures to survive and reproduce • Maximum • Obtain adequate nutrients • Dispose of wastes

  12. Why Cells Divide • Growth • Result of cells producing new cells by cell division • Differentiation – when cells develop into specialized shapes • Repair • Regeneration • Replace dead cells • Skin cells replace every 28 days

  13. Why Cells Divide • Reproduction • Asexual – offspring prod. by 1 parent • Ex. Bacteria, protists, plants and some animals • Cell division (mitosis) replicates chromosomes of one parent cell • Offspring are genetically identical to parent • Gives rise to diploid daughter cells (2N) • Sexual – offspring have combination of genetic material from 2 parents • Cell division (meiosis) results in offspring genetically different from parents • Results in 4 haploid (N) cells

  14. How Do Cells Divide? • Cell cycle – period from beginning of 1 cell division to beginning of the next cell division • 2 parts • Growth • Preparation • Cell divides in 2 stages • Mitosis (nuclear division) • Cytokinesis is (cytoplasm division)

  15. Cell Cycle Pg. 245

  16. Interphase • Part of cell cycle that occurs between divisions • Longest part of cell cycle – 90% of time • Stages • G1 or gap 1 – 1st stage • Characterized by growth and development • S or synthesis – 2nd stage • Chromosomes in nucleus replicate forming 2 identical structures called sister chromatids • Sister chromatids are visible as cell division begins • Joined together at a point called a centromere • Chromatin – thin, fibrous form of DNA and protein that make up a chromosome

  17. Phases of Mitosis • Prophase – 1st phase • Chromosomes condense and sister chromatids visible • Nuclear membrane and nucleolus break and disappear • Spindle fibers (from cytoskeleton) attach to centromere & begin to move sister chromatids toward center of cell

  18. Phases of Mitosis • Metaphase – 2nd phase • Chromosomes pull to center of cell and line up on the metaphase plate

  19. Phases of Mitosis • Anaphase – 3rd phase • Centromeres divide, spindle fibers pull chromatids apart and towards separate poles (ends) • Once separated, the chromatids are 2 identical sets of daughter chromosomes

  20. Phases of Mitosis • Telophase – 4th phase • 2 daughter nuclei are formed • Nuclear envelope forms around each set of chromosomes • Chromosomes uncoil to form chromatin • Animal cells – each new nucleus has a pair of centrioles outside its nuclear envelope

  21. Phases of Mitosis • Cytokinesis – cytoplasm divides • Begins during telophase as daughter nuclei form • Animal cell • Cell membrane at the center of parent cell folds inward = cleavage furrow • Furrow develops and 2 distinct cells with complete membranes are formed • Plant cell • Membrane fragments fuse to form a cell plate between the 2 new nuclei • A new cell wall forms between the membranes of the cell plate • A complete cell wall that divides the 2 daughter cells is formed

  22. Cytokenesis

  23. Regulating Cell Cycle • Cyclins • Proteins found in dividing cells • Regulate timing of cell cycle in eukaryotic cells • Figure 10-7 • Internal regulators – proteins that respond to events inside cell • External regulators – proteins that respond to events outside the cell • Cancer cells do not respond to either external or internal signals that regulate the growth of most cells

  24. Meiosis • Before meiosis • A diploid cell replicates its chromosomes • It will now consist of 2 sister chromatids joined by a centromere

  25. Phases of Meiosis • Meiosis I • Prophase I – each homologous pair of chromosomes attach to one another and equals 4 sister chromatids called tetrad • Metaphase I – chromosomes move to the center of the cells • Anaphase I – chromosomes are pulled to the poles • Telophase I – 2 daughter cells are formed that are haploid and consist of 2 sister chromatids • Each daughter cell now undergoes Meiosis II

  26. Phases of Meiosis • Meiosis II • Prophase II – sister chromatids begin to move to the center of the cell • Metaphase II – centromeres split in middle of cell • Anaphase II – individual chromosomes are pulled to the poles • Telophase II – 4 haploid daughter cells result • (2 from each Meiosis I daughter cell)

  27. Phases of Meiosis • Cytokenisis • In human males • All 4 haploid nuclei form sperm • In human females • Only 1 haploid nuclei forms an egg • The other 3 nuclei receive almost no cytoplasm and do not form gametes

  28. Meiosis Overview

  29. Regulating the Cell Cycle • Proteins found in dividing cells • Regulate timing of cell cycle in eukaryotic cells • Internal regulators – proteins respond to events inside • External regulators – proteins respond to events outside cell • CDKs • Involved in regulation of transcription of mRNA • Target for anti-cancer treatment

  30. Genes and Cancer • Causes of cancer • Mutations that change the genes that control cell growth and specializations • Can be inherited • Environmental factors • Combination of genetic and envir.

  31. Oncogene • A gene that causes a cell to become cancerous • Caused by a mutation in a growth factor gene • Caused by a DNA replication error • Multiple copies of a single growth factor gene • Caused by a change in a gene’s location

  32. Cancers Linked to Deletion Mutations

  33. Environmental Factors • Mutagens – factor in the envir. that can cause mutations • Radiation • Chemicals (tobacco prod.) • Carcinogen – agent that causes or tends to cause cancer by replacing or changing DNA • Tars • Chemicals in smoked meat • Viruses • Radiation (UV – sunlight) • Drugs • Coal tars (hair dyes)

  34. Karyotype • Picture of homologous pairs of chromosomes • Can show a various abnormalities • Nondisjunction – when chromosomes fail to separate during meiosis • Can result in too few or too many chromosomes

More Related