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Chapter 10 Chapter 10 Presentation Transcript

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