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DNA

DNA. What is DNA?. A code in the cell that contains the hereditary material The code is a chemical called deoxyribonucleic acid Every cell in your body contains DNA. DNA Structure. Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form by using an X-ray

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DNA

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  1. DNA

  2. What is DNA? • A code in the cell that contains the hereditary material • The code is a chemical called deoxyribonucleic acid • Every cell in your body contains DNA

  3. DNA Structure • Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form by using an X-ray • Similar to twisted ladder • James Watson & Francis Crick made a model of DNA molecule

  4. A DNA Model • Each side of the ladder is made of sugar-phosphate molecule • Called the “backbone” • Sugar = deoxyribose

  5. Rungs of the ladder are made up of nitrogenous bases • There are four types of bases • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T)

  6. Base Pairing • Adenine always pairs with Thymine A-T • Cytosine always pairs with Guanine C-G

  7. Copying DNA • The two sides of DNA unwind and separate • Each side becomes a pattern for a new DNA strand

  8. Genes • DNA in your cells stores the instructions for making proteins • Each chromosome contains hundreds or thousands of genes

  9. Making Proteins • Genes are found in the nucleus, but proteins are made on ribosomes in the cytoplasm • The code for making proteins are carried from the nucleus by RNA or Ribonucleic Acid

  10. Ribonucleic Acid • RNA is different from DNA • RNA is not a spiral, but one single strand • RNA has the bases A, G, C, and U not T • U = Uracil • Sugar is ribose, not deoxyribose

  11. DNA VS. RNA

  12. Types of RNA • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)

  13. Controlling Genes • Each cell only uses some of the thousands of genes to make proteins • Cells must be able to control genes by turning some genes on and others off

  14. Mutations • Permanent changes in the DNA sequence of a gene • These happen when the DNA is not copied correctly • They cause incorrect proteins to be made

  15. Causes of Mutations • X-rays • Sunlight • Some chemicals

  16. Results of Mutations • Some mutations are beneficial • They add variety to the species • Many mutations are harmful and can cause death • Cystic Fibrosis • Some mutations have no effect on the organism

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