AP Biology The Discovery and Structure of The Genetic Material called “DNA”

AP Biology Frederick Griffith finds a “Transforming Factor” “Transformation” something in heat-killed bacteria could still transmit disease-causing properties live pathogenic strain of bacteria live non-pathogenic strain of bacteria mice diemice live heat-killed pathogenic bacteria mix heat-killed pathogenic & non-pathogenic bacteria mice livemice die A.B. C. D.

AP Biology So what is this “transforming factor”  Deoxyribonucleic Acid  or what we have been calling DNA  every single organism on our planet has its own DNA molecule  “blueprint of life” why is it called this? Franklin WilkinsPauling

AP Biology Watson and Crick Crick Watson  Watson & Crick  developed double helix model of DNA

AP Biology DNA is a Nucleic Acid Nucleic Acids are made from Nucleotides A Nucleotide has three parts: 1. phosphate group 2. sugar molecule (Deoxyribose) 3. nitrogen-containing base (A,T,C,G) phosphate group nitrogen-containing base sugar You will have to recognize nucleotide shape on EOC!!!!!!

AP Biology A closer look at the different nitrogen bases!  4 different nucleotides  A – adenine T – thymine  C – cytosine G - guanine nucleotide – nucleotide – nucleotide – nucleotide phosphate sugar N base

AP Biology Making the DNA Molecule  Base pairing rules:  adenine (A) = thymine (T) “AT”  guanine (G) = cytosine (C)

AP Biology Don’t forget about the other nucleic acid  RNA is different from DNA molecules  single strand of nucleotides  sugar is ribose  Thymine (T) is replaced with Uracil (U)

AP Biology Copying DNA “DNA Replication” How do cells make new DNA molecules?

AP Biology Remember why DNA must be duplicated… nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes Cells divide so each cell needs own copy of DNA

AP Biology But how is DNA copied?  Its called replication of DNA  DNA unzips and each side serves as a template for a new strand

AP Biology DNA Replication  Step 1: DNA Strands “unzip” at the weak bonds between bases  Enzyme used - helicase helicase

AP Biology DNA Replication DNA polymerase  Enzyme  DNA polymerase  adds new bases DNA bases in nucleus Step 2: Complementary strand is made

AP Biology DNA Replication  Result is 2 exact copies of DNA to split between new cells DNA polymerase DNA polymerase

AP Biology DNA replication starts at many points in eukaryotic chromosomes. Called “replication bubbles” Replication is fast and accurate.

AP Biology DNA Polymerase Copying DNA  Build daughter DNA strand direction opposite direction  anti-parallel - think divided highway

AP Biology So lets sum it up