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  1. 1. Genetics, DNA, and Heredity
  2. 2. What is Inheritance? <ul><li>Inheritance – process of passing on characteristics (traits) from parent to offspring. </li></ul>
  3. 3. Gene <ul><li>Gene – small piece (segment) of DNA that codes for a specific trait. </li></ul><ul><li> - Trait - eye color, hair color, height, etc. </li></ul><ul><li> </li></ul>
  4. 4. <ul><li>Genes pass on hereditary material to offspring . </li></ul><ul><li>Asexual reproduction – all genes come from one parent (mitosis). </li></ul><ul><li>- Offspring identical to parent. </li></ul><ul><li>Sexual reproduction – half genes from mom and half from dad (meiosis). </li></ul><ul><li>- Offspring are different from parent. </li></ul>
  5. 5. Where are Genes? <ul><li>Genes are found on chromosomes  nucleus . </li></ul><ul><li>- Each cell nucleus in your body </li></ul><ul><li>has thousands of genes on the 46 chromosomes. </li></ul>
  6. 6. Where are Genes?
  7. 7. What is DNA? <ul><li>DNA - D eoxyribo N ucleic A cid </li></ul><ul><li>Long molecule used in storing hereditary (genetic) information makes up genes . </li></ul><ul><li>- “blueprints” that build an organism. </li></ul>
  8. 8. Structure of DNA <ul><li>DNA is made up of thousands of smaller molecules called nitrogenous bases . </li></ul>
  9. 9. <ul><li>a. Adenine (A) </li></ul><ul><li>b. Guanine (G) </li></ul><ul><li>c. Cytosine (C) </li></ul><ul><li>d. Thymine (T) </li></ul><ul><li>These 4 bases exist in pairs : </li></ul><ul><li>Guanine-Cytosine (G-C) and Adenine-Thymine (A-T) </li></ul><ul><li>( G ood C ouples are A lways T ogether ) </li></ul>4 Kinds of Nitrogenous Bases
  10. 10. Shape of DNA <ul><li>Double Helix – looks like a twisted </li></ul><ul><li>ladder with two strands of DNA wrapped </li></ul><ul><li>around each other. </li></ul>
  11. 11. The “Ladder” (Draw Me!) Nitrogenous bases form the “steps” of the ladder
  12. 12. “ Packaging” DNA <ul><li>The nucleus contains the chromosomes . </li></ul><ul><li>Chromosomes contain lots of DNA strands which make up genes . </li></ul>
  13. 13. DNA Replication <ul><li>Before a cell divides (mitosis or meiosis) it must replicate , or copy, its DNA. </li></ul><ul><li>- This makes sure that all cells have copies of the DNA. </li></ul>
  14. 14. How is DNA Replicated? <ul><li>DNA is replicated in 3 steps : </li></ul><ul><li>Original DNA molecule unzips </li></ul><ul><li>2 new strands begin to take form </li></ul><ul><li>Two identical DNA strands are formed </li></ul>
  15. 15. 1. Unzip original DNA <ul><li>Original DNA molecule becomes separated ( unzips ). </li></ul>
  16. 16. 2. Expand Two New Strands <ul><li>Each original strand now becomes a template (model) for a new strand of DNA. </li></ul>
  17. 17. Base pairs are added to new strand using the same rules G ood C ouples A lways T ogether. Original A T T G New T A A C New Strand
  18. 18. 3. Two Identical DNA Molecules are Formed <ul><li>Two new DNA molecules formed, each with 1 original strand and 1 new strand. </li></ul>
  19. 19. Heredity and Traits <ul><li>Proteins decide which traits will be shown by the offspring . </li></ul><ul><li>DNA codes for which amino acids will make the proteins . </li></ul>
  20. 20. What Organelle Makes Proteins? <ul><li>The organelles that assemble proteins from amino acids are the ribosomes. </li></ul>
  21. 21. How Does DNA’s Directions Get to the Ribosomes? <ul><li>A messenger molecule (RNA) copies information from the DNA . </li></ul><ul><li>The messenger molecule (RNA) goes to the ribosome . </li></ul><ul><li>The ribosome collects amino acids and assembles the proteins in the proper order. </li></ul>
  22. 22. Changes in Heredity- Mutations
  23. 23. Nothing is perfect… <ul><li>Mutation – any changes (alterations) in the sequence of DNA that affects genetic information and the appearance of offspring. </li></ul><ul><li>Caused by: UV Light, X-Rays, etc. </li></ul>
  24. 24. Types of Mutations <ul><li>Gene mutation – a mutation that occurs in a single gene and affects one trait. </li></ul><ul><li>Ex: Eye color, Sickle cell Anemia, Hemophilia </li></ul><ul><li>Chromosome mutation – a mutation that occurs in many genes and affects many traits at once. </li></ul><ul><li>Ex: Down Syndrome (an extra 21 st chromosome) </li></ul>
  25. 25. How Can Mutations Affect an Organism? <ul><li>Body cell mutations can cause cancer . </li></ul><ul><li>- only the individual is affected. </li></ul><ul><li>Gamete cell mutations affect the egg and the sperm . </li></ul><ul><li>- all offspring of the individual can be affected. </li></ul>
  26. 26. Gene Expression <ul><li>An individual’s trillions of body cells all come from one cell ( zygote ). </li></ul><ul><li>In differentiation the cells become different tissues . (ex: skin, muscle, organ) </li></ul><ul><li>Certain cells will “turn on” or activate only the genes they need. This is called gene expression. </li></ul>
  27. 27. Factors that Affect Gene Expression <ul><li>The internal and external environment of a cell can influence which genes are “turned on”. </li></ul><ul><li>Ex: - Hormones can “tell” a cell to activate a specific gene. </li></ul><ul><li> - Outside temperature changes fur color in rabbits. </li></ul>