DNA Deoxyribonucleic acid Lesson 2 Goal 1: to describe DNA in terms of its structure, location, and function Goal 2: to compare purine bases and pyrimide bases

What is DNA the nucleic acid that stores and passes on the genetic information from one generation to the next the source of genetic variation the source of diversity Where is DNA? • DNA is found in the nucleus of cells and does not leave!

What is dna composed of? DNA is composed of units called nucleotides which are composed of three sub-molecules: 1. a 5 carbon sugar (deoxyribose) 2. a phosphate group 3. nitrogenous base (purine or pyrimidine

Types of bases PURINES: PYRIMIDINES have 2 rings Have a single ring Thymine , cytosine, (also Uracil only in RNA) Memory trick: CUT the Py PURINES: have 2 rings adenine & guanine Memory trick: 2 rings are pure silver (Ag)

Complimentary base pairs DNA is composed of two complementary strands of nucleotides joined by hydrogen bonds. According to Chargaff’s rules: Adenine with Thymine (A-T or T-A) They join with 2 hydrogen bonds   Cytosine with Guanine (C-G or G-C) They join with 3 hydrogen bonds Notes: purine always pair with pyrimidine 2 apples in the tree, 3 cars in the garage

What does dna look like? DNA twists into a double helix which resembles a twisted ladder The backbone (rails of the ladder) are made of alternating Sugars and phosphate groups The steps (rungs) are made of the nitrogenous bases. The two strands are anti-parallel—they run in opposite directions

Complete the second strand of DNA Complete the second strand of DNA. Show the number of bonds between each. A T G T G A T C C A C G T A C A C T A G G T G C  

Functions of the dna DNA directs the machinery of a cell to make specific proteins and, therefore, DNA indirectly controls all of the functioning of all living things. Protein Synthesis = Cell Control DNA _stores the hereditary information of an individual DNA has the ability to mutate (change). This allows for new characteristics and abilities to appear which may help an individual to survive and reproduce (Adaptation – Survival of the Fittest_) Evolution Self-replication: DNA has the ability to Copy itself DNA Replication & Cell Cycle

Cell Division Protein Synthesis DNA Replication

How do we know James Watson and Francis Crick 1953—they determined the double helix structure Rosalind Franklin (1920-1958)- chemist and X-ray crystallographer who made contributions to the understanding of the molecular structures of DNA, RNA Complete the practice, check your answers, then do the quiz on classroom