Fun Times with the Double Helix

 Set up notes page as shown  Fold colored paper as shown  Record new vocab words and review these at home  Use different colored pencils

 Itself is not alive…  Exists for only one reason… to make more DNA  2 meters squeezed into each cell ~2o million km!  Holds the instructions to make and maintain you.  Contains roughly 3.2 billion letters- 10 3,480,000,000 combinations  Is 99.9% identical to everyone else’s DNA  Is 0.1% completely and utterly unique to you.

 James Watson and Francis Crick- discovered the structure of DNA– the double helix

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 4 types of nucleotides, A,T, C, G  Complementary base pairing:  A = T  C = G

 DNA inside nucleus makes copy of itself during _____ stage of _______________.  Part of the DNA helix unwinds (by enzyme “helicase”) when H+ bonds between nitrogenous bases are broken.

 Each strand serves as a pattern for a new strand of DNA  Enzyme DNA Polymerase moves along each separate strand and matches bases (A, C, T, G) on each strand to a new base that is “floating” inside the nucleus.

 H+ bonds reform between bases…

 Each strand of DNA serves as a template for a new strand.  The replicated DNA is made of one old strand and one new strand

How does a cell interpret DNA? Simulation:  Group A: Design a structure using all the materials in the ziplock bag.  Devise a way to communicate with Group B how to duplicate this design… no words, no pictures… all blueprints stay at Group A site.

From DNA to messenger RNA

 Making a protein (polypeptide) begins with making mRNA (messengerRNA) inside the nucleus.  RNA is also a “nucleic acid”  is single-stranded  has “uracil” (U) instead of thymine  has 5C sugar “ribose”

 Step 1: DNA strand separates at a gene spot on DNA.  Only 1 strand of DNA will serve as a template- starts at a “promoter”  Step 2: Enzyme “RNA polymerase” matches RNA bases with DNA bases: A, U, C, G  Step 3: Enzymes link RNA nucleotides together into a single-strand of RNA.

 Step 4: mRNA leaves nucleus with code for protein and moves to ribosomes where the protein will be made.  Important editing is required of mRNA:  Introns: cut-out connected sequences  Exons: expressed sequences spliced together- final edited RNA

 ture=relmfu

 There are actually many types of RNA.  In most cells three kinds of RNA are critical to the making of proteins.  mRNA – “messenger RNA” carry copies of the instructions for the proteins from the DNA to the ribosomes  rRNA – “ribosomal RNA” are part of the ribosomal structure  tRNA - “transfer RNA” transfers the amino acids to the ribosomes to make the protein

 Making of proteins is called “protein synthesis”  Instructions for each protein comes from the mRNA in 3-base messages called “codons”  Codons are translated in the ribosomes. mRNA attaches to the ribosome (rRNA)

 “Translation” is the decoding of the message from the mRNA into a polypeptide chain (protein).  The tRNA is a cloverleaf-shaped molecule that has on one end a complementary “anticodon” and on the other end an amino acid.  Example: codon AAA, anticodon UUU or lysine

 As the codons from the mRNA are “read” inside the ribosome and the tRNA delivers one amino acid at a time…  these amino acids bond together with “polypeptide” bonds …  the “language” of mRNA instructions is called the Genetic Code…  How can 3 base codons make 20 amino acids? (4 x 4 x 4) = 64 possibilities