Objectives To explain how instructions in DNA lead to different cells and result in cells being able to perform certain tasks in an organism Identify the building blocks and nitrogenous bases (A, T, G, C and U) of nucleic acids

Who Discovered DNA? 1952 Rosalind Franklin-studied DNA molecule using x-ray diffraction 1953 Watson and Crick- developed double helix model

What is DNA? Although the environment can influence how an organism develops, DNA determines the organism’s TRAITS. Determines the structure of the proteins. Contains the instructions for LIFE! DEOXYRIBONUCLEIC ACID! Prokaryotic and Eukaryotic cells depend on DNA to determine function.

What does DNA look like? DNA – Phosphate group One phosphorous atom Four O 2 atoms – Deoxyribose (simple) sugar Give DNA it’s name – Nitrogenous Base Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

DNA Structure Nucleotides make up the DNA Each nucleotide is held together by hydrogen bonds! Hydrogen bonds are easily broken.

DNA Structure Double Helix Twisted ladder structure Sides have alternating phosphate sugar groups “Rungs of a DNA ladder” “Chargoff’s rule” A = T & C = G (Complementary Base Paring)

DNA Replication DNA must be copied before the cell can divide (mitosis or meosis) Without replication, new cells would only have ½ the DNA of their parents. Survival, growth, and reproduction would be impossible Prokaryotic and Eukaryotic cells depend on DNA replication to ensure each daughter cell will receive same genetic instruction as parent cell.

Because of base pairing, we can predict the sequence of bases on a different strand. During replication, each strand serves as a template (or pattern) Enzymes break apart the DNA at the hydrogen bonds. The old strand is paired with each complementary base generating a complementary strand. DNA runs 3” to 5” (leading strand) ; DNA replicates 5” to 3” (lagging strand)

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Why does sequence matter? The sequence of nucleotides creates the specific genetic information. Different sequence = different function. ATTGAC is not the same as TCCAAA. The closer a sequence is related to another, the more similar the organisms are to one another

Knowledge Check What is DNA? DNA determines an organism’s ____________ What does DNA stand for? What are the 4 nitrogenous bases? Pair the following nitrogenous bases with their matching bases: AAAT CGATATC TTCCGCT