Characteristic of Life!! DNA is found in all living things and has the same structure!
Nucleic Acids Examples - DNA and RNA Slide 2.35
DNA Location and Function Location – Nucleus (Eukaryotes) Function – contains the genetic instructions for the development and function of living things. Slide 3.37
Monomer = Nucleotides DNA is made up of two long chains of nucleotides. Each nucleotide has three parts. phosphate group deoxyribose sugar nitrogen-containing base (A,T,C,G) There are four different nucleotides Each contain a different nitrogen base. phosphate group deoxyribose (sugar) nitrogen-containing base
Structure = Double helix Double = two strands connected Helix = twisted Looks like a “twisted ladder”. Main Parts Backbone Phosphate and 5 carbon sugar Nitrogen bases
Four Nitrogen Bases Adenine, Thymine, Cytosine, and Guanine Can be either a single or double carbon ring Pyrimidine = Single Carbon Ring Purine = Double Carbon Ring
DNA Discovery James Watson & Francis Crick Determined the three-dimensional structure of DNA. Identified the double helix structure with a sugar-phosphate backbone on the outside and bases on the inside.
Other Contributors Rosalind Franklin’s x-ray images suggested that DNA was a double helix of even width. Erwin Chargaff found that nucleotides can be found in even ratios. Chargaff’s Rules Adenine to Thymine Cytosine to Guanine
Nucleotide Paring Rules (Complementary Base Pairing) The base-pairing rules dictate how nucleotides always pair up in DNA. Since a pyrimidine base (single ring) pairs with a purine base (double ring), the helix has an even width. Adenine pairs with Thymine Cytosine pairs with Guanine C G T A
Nucleotide Bonding Backbone is connected by covalent bonds. Nitrogen bases are connected by hydrogen bonds. hydrogen bond covalent bond
DNA Replication – The process of copying a strand of DNA Why do cells need to make a copy of their DNA? Occurs in the nucleus during interphase (Synthesis) Is a “semi-conservative” process The original (parent) DNA strand is used as a “Template” to make the new DNA strand Results in 2 strands of DNA that are half old and half new (2 semi conservative DNA molecules)
DNA Replication: Semi-conservative DNA helicase uncoils and unzips DNA New nucleotides line up next to both old (parent) chains of the DNA
DNA Replication – cont’d DNA polymerase binds the new nucleotides together and “proofreads” the new strands for errors. Results in 2 semi-conservative strands of DNA
DNA Replication Final Result – 2 Semi-Conservative Strands of DNA
DNA: the Genetic Code is carried in Triplets Genetic code = Order of nitrogenous bases Gene: a DNA segment that carries the information for building a protein.
Reading DNA DNA is read in sets of three nucleotides called a triplet! 1 DNA triplet codes for 1 amino acid in a protein