DNA and RNA

DNA and RNA

1. Structure of DNA

   • Nucleotides consists of a phosphate group, a sugar and a nitrogen-containing base
     • Four different bases
       • Adenine(A) and Guanine(G) are called purines
       • Thymine(T) and Cytosine(C) are called pyrimidines
       • "The Attorney General is Pure"
     • Sugar used in DNA is called Deoxyribose
   • Base Pair
     • Adenine and Thymine both form two weak hydrogen bonds
     • Guanine and Cytosine form three hydrogen bonds
   • The Double Helix
     • James Watson & Francis Crick
     • The double-stranded DNA molecule is wound into a double spiral

2. DNA Replication

   • Takes place in the nucleus during interphase
   • Results in a single-stranded chromosome forming two identical strands that are held together at the centromere
   • 1: the double helix unwinds
     • 2: enzymes break the hydrogen bonds
       • 3: the complementary strands move apart
         • 4: nucleotides move from cytoplasm into nucleus and attach to their complementary bases on the exposed strands
           • 5: new strands contain exactly the same sequence of bases. Each new stretch of DNA re-forms into a double helix

3. The Genetic Code

   • A triplet is a sequence of three bases in a row
   • A codon is a triplet that acts as a code for an amino acid
   • Genes are composed of long sequences of DNA bases. Genes cause a sequence of amino acids to be assembled to form a protein

4. DNA Profiles

   • A DNA profile is a unique pattern of DNA from one person that is compared with the DNA profile of another person
   • 1: DNA Isolation: DNA is extracted using a type of detergent which breaks down the cell and nucleus, releasing the DNA
     • 2: Cut the DNA into Fragments using a restriction enzyme
       • 3: Separate the Fragments based on their lengths using process called gel electrophoresis. DNA places into a el and electric current is applied
   • Uses of DNA profile
     • Crime
     • Medical
       • Paternity

5. Genetic Screening

   • Genetic Screening is a test of a person's DNA to see if an altered gene is present
   • Mutated genes are the cause of many genetic disorders such as:
     • Cystic Fibrosis (where fluid can't be removed from lungs)
     • Albinism (inability to form the pigment melanin)
   • Ethical Problems
     • If an embryo has disorder, may encourage abortion
     • Insurance companies may be informed of results

6. RNA

   • CATGUT: where CATG are the bases in DNA, and U replaces T in RNA

7. Protein Synthesis

   • Protein Synthesis is the making of protein using amino acids and the code in mRNA
   • Transcription is converting the code on DNA to a code on mRNA
   • Translation is converting the code from RNA to form a protein
   • 1: double helix unwinds at site of gene that is to form protein
     • 2: Transcription occurs, sequences of bases on DNA used to form a complementary strand of mRNA
       • 3: mRNA strand moves out of nucleus into cytoplasm
         • 4: mRNA strand moves into a ribosome
           • 5: large number of tRNA molecules in cytoplasm, each carries a specific amino acid
             • 6: Triplets/codons on mRNA attract complementary triplets on tRNA molecules
               • 7: Amino acids are detached from their tRNA and bonded together in ribosomes to form a new protein
                 • 8: protein folds into correct 3D shape to function properly

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