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Chapter 10


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Chapter 10

  1. 1. Chapter 10 DNA, Nucleic Acids and Protein Synthesis
  2. 2. Structure of DNA <ul><li>DNA is a polymer. </li></ul><ul><li>DNA is made from monomers called nucleotides. </li></ul><ul><li>A nucleotide is made of three parts: deoxyribose (sugar), phosphate group, and a nitrogen-containing base </li></ul>
  3. 3. Nitrogenous Bases <ul><li>DNA is made from 4 bases. </li></ul><ul><li>Adenine, guanine, cytosine and thymine. </li></ul><ul><li>They are represented A, G, C, T. </li></ul><ul><li>Adenine and Guanine are classified as purines and contain two rings of carbon. </li></ul><ul><li>Thymine and Cytosine are classified as pyrimidines and contain one ring of carbon. </li></ul>
  4. 5. The Double Helix <ul><li>In 1953, James Watson and Francis Crick suggested a model for the structure of DNA. </li></ul><ul><li>The shape is called a Double Helix and is a spiral. </li></ul>
  5. 7. The Double Helix <ul><li>Other scientists contributed to the discovery of the double helix. </li></ul><ul><li>Rosalind Franklin took pictures of DNA crystals and revealed the helix shape. </li></ul><ul><li>Maurice Wilkins assisted Rosalind Franklin in her research. </li></ul><ul><li>The double helix was found to be linked together by hydrogen bonds. </li></ul>
  6. 8. Base Pairing <ul><li>Cytosine always pairs with guanine using 3 hydrogen bonds. </li></ul><ul><li>Adenine always pairs with thymine using 2 hydrogen bonds. </li></ul><ul><li>This base pairing rule is important because when DNA is replicated, all copies must be the same. </li></ul>
  7. 10. DNA Replication <ul><li>The process of copying DNA is called DNA Replication. </li></ul><ul><li>Replication can begin and end at many points on the molecule simultaneously. </li></ul><ul><li>Step 1: Helicase separates the double helix into two strands. </li></ul><ul><li>Step 2: DNA polymerase binds to the separated strands and constructs a new strand based off the old one using base pairing rules. </li></ul><ul><li>Step 3: The Double Helix winds up again. </li></ul>
  8. 13. Accuracy and Repair <ul><li>The process of DNA Replication occurs with a high degree of accuracy. </li></ul><ul><li>Sometimes a mutation can cause a change in a base pair. </li></ul><ul><li>The body contains enzymes to help find the mistakes and repair the errors. </li></ul><ul><li>Some errors are missed and have serious consequences for new cells. </li></ul><ul><li>Mutations can occur because of chance, chemicals, ultraviolet light and other agents. </li></ul>
  9. 14. RNA <ul><li>RNA is similar to DNA because it is made of nucleotides. There are some differences though. </li></ul><ul><li>Difference 1: RNA contains the sugar ribose. </li></ul><ul><li>Difference 2: RNA is single stranded all the time. </li></ul><ul><li>Difference 3: RNA does not contain thymine but has uracil instead. </li></ul>
  10. 16. Types of RNA <ul><li>RNA has three types. </li></ul><ul><li>Messenger RNA (mRNA) is a single uncoiled chain that carries information from DNA in the nucleus to the cytoplasm to make proteins. </li></ul><ul><li>Transfer RNA (tRNA) is a coiled single chain shaped like a T that binds to specific amino acids. </li></ul><ul><li>Ribosomal RNA (rRNA) are in a glob shape and make up ribsomes where proteins are made. </li></ul>
  11. 17. Transcription <ul><li>One function of RNA is to carry genetic information from DNA in the nucleus to the cytoplasm when it can be used to make proteins. </li></ul><ul><li>The process by which genetic information is coped from DNA to RNA is called transcription. </li></ul>
  12. 20. Steps of Transcription <ul><li>Step 1: DNA unwinds. </li></ul><ul><li>Step 2: RNA polymerase binds to the DNA and begins to bring in RNA nucleotides. </li></ul><ul><li>Step 3: RNA is paired with the DNA according to base pair rules until an entire RNA strand is made. </li></ul><ul><li>Step 4: The RNA is released and the DNA winds up again. </li></ul><ul><li>All three types of RNA can be made this way. </li></ul>
  13. 21. Splicing <ul><li>Once the mRNA is made from the DNA, it must be edited to remove information that is not required for protein synthesis. </li></ul><ul><li>Raw mRNA is made of introns and exons. </li></ul><ul><li>During splicing, introns are removed and the exons merge together. </li></ul>
  14. 23. Protein Synthesis <ul><li>Proteins are polymers or polypeptides. </li></ul><ul><li>The proteins are made of monomers called amino acids. </li></ul><ul><li>There are 20 different amino acids. </li></ul><ul><li>During protein synthesis, mRNA is translated into specific amino acids. </li></ul><ul><li>The genetic information necessary to make amino acids is in the form of triplets called codons. </li></ul><ul><li>Codons are three nucleotides together as a set. </li></ul><ul><li>All living beings contain codons and make proteins the same way. This evidence supports that all living creatures are related. </li></ul>
  15. 25. Translation <ul><li>The process of assembling proteins from information coded in mRNA is called translation. </li></ul><ul><li>mRNA leaves the nucleus and then migrates to the cytoplasm to dock with ribosomes. </li></ul><ul><li>Amino acids float freely in the cytoplasm waiting to be picked up by tRNA molecules. </li></ul>
  16. 26. Steps to Translation <ul><li>Step 1: mRNA moves from the nucleus to the cytoplasm. </li></ul><ul><li>Step 2: mRNA docks with one or many ribsomes. </li></ul><ul><li>Step 3: tRNA each with specific anticodons dock with the codons on the mRNA starting with the start codon AUG. </li></ul><ul><li>Step 4: As each tRNA docks, it brings with it an amino acid. </li></ul><ul><li>Step 5: The amino acids bind together and become long chains called proteins. </li></ul><ul><li>Step 6: Once the stop codon is reached, the protein breaks off and leaves the cell to be used. </li></ul>
  17. 30. Problems During Synthesis <ul><li>As with all mechanisms and processes, these can have problems if a mutation changes a base. </li></ul><ul><li>Once the base of a DNA molecule is changed, that changes the mRNA which in turn changes the protein made. </li></ul><ul><li>This can cause serious illness and disease or it may cause nothing. </li></ul>