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Unit V – Genetics & Heredity Cell Cycle & Mitosis

The Cell Cycle & DNA The Story of the Nucleus. Unit V – Genetics & Heredity Cell Cycle & Mitosis. Introduction to Cell Division. Why do we need more cells? Recall: can’t have bigger cells…need more cells) To grow, repair, develop, reproduce. Introduction to Cell Division.

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Unit V – Genetics & Heredity Cell Cycle & Mitosis

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  1. The Cell Cycle & DNA The Story of the Nucleus Unit V – Genetics & HeredityCell Cycle & Mitosis

  2. Introduction to Cell Division • Why do we need more cells? • Recall: can’t have bigger cells…need more cells) • To grow, repair, develop, reproduce

  3. Introduction to Cell Division • How do we get more cells? • Recall: “cells come from pre-existing cells” • Cells divide into two

  4. Introduction to Cell Division • Before cells can divide, what must they do to prepare? • Grow larger • Grow more organelles • Double their DNA

  5. The Cell Cycle

  6. The Life Cycle of a Cell • Interphase • This is where cells grow and copy their DNA (chromosomes) • Has 3 parts: • G1 (growth) • S (doubling chromosomes) • G2 (growth) Note: in this phase, DNA is in the form of very thin strands called chromatin…hard to see

  7. The Life Cycle of a Cell • Mitosis • Phase responsible for splitting cell into 2 exact copies (new cells)

  8. The Life Cycle of a Cell • Interphase • Nucleus visible w/ nucleolus • can’t see chromosomes • DNA doubles; cell grows • Prophase • Chromosomes form (coil) • Nuclear membrane disappears • Metaphase • Chromosomes line up in the middle (equator) of cell

  9. The Life Cycle of a Cell • Anaphase • Sister chromatids separate & migrate away from each other • Telophase • Cell “furrow” or cell plate appears • Nuclei reappear in each new cell • Cytokinesis • Cytoplasm splits to separate cells

  10. The Life Cycle of a Cell Name the phase: Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

  11. Quiz • 1. Why are the events of Interphase important? • 2. In which phase of mitosis do the sister chromatids separate? • 3. Why can’t chromosomes be seen in the cell during Interphase? • 4. In which phase of mitosis is the nucleus broken down? • 5. Why is mitosis needed? (What is its purpose?)

  12. Quiz • 6. Where in the cell does photosynthesis take place? • 7. What is the purpose of photosynthesis? • 8. Where in the cell does cellular respiration occur? • 9. What is the purpose of cell respiration? • 10. On the cellular level, why do we need to breathe?

  13. DNA Structure • What is the difference between chromosomes, genes, and DNA? • Chromosomes are coiled up rods of DNA • Genes are sections of DNA that code for traits

  14. DNA Structure • What does DNA look like? • Double helix…2 strands coiled around each other • Backbone is made up of alternating sugar and phosphate groups Deoxyribose (sugar) Phosphate

  15. DNA Structure • What does DNA look like? • Connection points are pairs of bases • Adenine (A), guanine (G), cytosine (C), thymine (T) • A always pairs with T • C always pairs with G

  16. DNA Structure

  17. How does DNA “control”? • The order of bases spells out the plans for “how to build you”. • The bases work in groups of three. • This group is called a “DNA triplet”

  18. How does DNA “control”? • How can 4 bases control everything in our cells (and thus everything in an organism?) • The 4 DNA bases are like • letters in the alphabet • The DNA triplets are like • words • The entire gene is like • a sentence

  19. How does DNA get copied? • DNA Replication • DNA unwinds • New nucleotides bind to old strands • The strands coil back up forming 2 instead of 1

  20. DNA Quiz • 1. If the green base is adenine (A), which base is the red? • 2. What structure is represented by the blue section? • 3. Which structure is represented by the teal section?

  21. DNA Quiz • 4. Which part of DNA actually holds the code? • 5. During which phase of the cell cycle does DNA copy itself? • 6. Describe how DNA is able to copy itself. Be specific! • 7. What is the difference between a chromosome and a gene?

  22. Unit IV – Cell Function Part 3 – Protein Synthesis The Story of the Ribosome

  23. How do we get actual traits from DNA? • Our heritable traits are determined by the proteins that we make (including our enzymes) • Example: a gene in DNA has directions for how to build melanin…melanin gives you your skin coloration gene  protein  trait

  24. Rules for Building a Protein • DNA cannot leave the nucleus • Must have a messenger to get code from DNA & take it to ribosome • Proteins are made from amino acids (AA’s)

  25. Both DNA & RNA are needed to build a protein Although they are similar there are some important differences: • DNA • 2 strands • Deoxyribose sugar • Thymine (T) binds with A • RNA • 1 strand • Ribose sugar • Uracil (U) binds with A

  26. RNA • How does RNA differ from DNA? • 1 strand • U not T • ribose

  27. What types of RNA are there? • mRNA (messenger RNA) - copies the directions from DNA & takes them to the ribosomes • tRNA(transfer RNA) - picks up certain AA’s & brings them to the ribosome for assembly

  28. How does mRNA know how to copy DNA? • DNA triplets match up with sets of 3 mRNA bases…called codons • If DNA says this…what will mRNA be? • TAC – GGA – CTT – GAT – ACA – ATT • AUG – CCU – GAA – CUA – UGU – UAA

  29. How does mRNA know which AA’s to assemble? • tRNA carries a code of 3 letters called an anticodon that pairs up with the codons of mRNA • If mRNA says this…what will the tRNA’s be? • AUG – CCU – GAA – CUA – UGU – UAA • UAC – GGA – CUU – GAU – ACA - AUU

  30. How does mRNA know which AA’s to assemble? • Each tRNA can only pick up one specific AA • When it matches up with the anticodon, it brings along its AA • If mRNA says this…what will the AA’s be? • AUG – CCU – GAA – CUA – UGU – UAA • Met – Pro – Glu – Leu – Cys - Stop

  31. Use a chart to find order of AA’s: • Which AA is: • CGU • Arg • AUC • Iso

  32. Use a chart to find order of AA’s: • Which AA is: • UCA • Ser • GAG • Glu

  33. Protein Synthesis • Transcription (“to copy”) • mRNA goes to nucleus & copies DNA code for one gene • mRNA takes the copy to the ribosome in the cytoplasm

  34. Protein Synthesis • Translation(“DNA” to “protein”) • Ribosome uses mRNA copy to look for certain tRNA’s (ones with correct anticodon) • tRNA’s pick up specific AA’s & bring them to ribosome when they are needed • AA’s are pulled off tRNA’s & attached to the growing protein chain

  35. Protein Synthesis • Name the process: Transcription Translation

  36. Protein Synthesis • Name the parts: DNA mRNA tRNA Amino Acid Protein Ribosome

  37. Gene Mutations • Sometimes mutations (errors) occur • Changes in DNA code may be harmful, helpful, or have no effect • If instructions for cell division affected, can lead to cancer (uncontrolled cell growth)

  38. Gene Mutations • May occur in reproductive cells • Affects offspring, not you • …Or in “body cells” • Affects you, not offspring

  39. Gene Mutations • Point Mutations • A change in a single DNA base • THE DOG BIT THE CAT • THE DOG BIT THE CAR • This may or may not change the protein that is made (some AA’s have more than one code)

  40. Gene Mutations • Point Mutations

  41. Gene Mutations • Frameshift Mutations • AA’s shift when a single base is inserted or deleted • THE DOG BIT THE CAT • THE DOB ITT HEC AT (deletion) • THE DOQ GBI TTH ECA (insertion)

  42. Gene Mutations • Frameshift Mutations

  43. The End

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