What is DNA? Ms. Kim Deoxyribonucleic Acid • Cells contain information…. But how is this information stored? The Discovery of the Structure of DNA https://www.youtube.com/watch?v=V6bKn34nSbk What are chromosomes? https://www.youtube.com/watch?v=IePMXxQ-KWY • Human karyotype (picture of the chromosomes) Chromosomes • Long threads of DNA • Carry genetic information of cell • Information determines what proteins are made • Made up of many genes What are genes? • Genes are segments of chromosomes that contain the code required to direct the manufacture of a polypeptide or RNA molecule DNA • Two complementary strands (double helix) • Sugar-phosphate backbone • Made up of four types of nucleotide: A,T,C, and G • Complementary base-pairing: A-T, C-G • The genetic information of living things • Able to self-replicate DNA Structure • Double helix: like a twisted ladder – Sugar and phosphate form the “sugar phosphate backbone” – Nitrogen bases bond in the middle with weak hydrogen bonds – All other bonds are strong covalent bonds Creating the Helix • The four nucleotides are either purines, which are double-ringed structures, or pyrimidines, which are single-ringed structures. These are referred to as bases. • The four bases are: Adenine (A) – a purine Cytosine (C) - a pyrimidine Guanine (G) – a purine Thymine (T) – a pyrimidine https://www.youtube.com/watch?v=Xjja9w0Z8tA The Characteristics of DNA • Each of its double strand is a single molecule • Each strand is a pattern made from four parts called nucleotides • The two strands are joined together by hydrogen bonds, like rungs of a ladder • The two strands wind around each other to create a double helix The Functions of DNA • Replication – which means the DNA must be copied every time a cell divides • Expression – DNA guides the characteristics that determine all biological traits of a specific organism. E.g) Red hair, blue eyes in human, or the various colors of horses. Complementary nucleotides • These create base pairs formed by complementary nucleotides (purine with pyrimidine) connected by hydrogen bonds. Adenine will only pair with thymine, and cytosine will only pair with guanine. The hydrogen bonds cause the twisting that is characteristic of a double helix. Lesson Summary • DNA stands for deoxyribonucleic acid. It is the master molecule in every cell, containing genetic information. The main characteristics of DNA include being a protein, each strand is a single molecule, each strand is a pattern made of nucleotides, the two strands are joined together by hydrogen bonds, like rungs on a ladder, and the two strands wind around each other to create a double helix. • DNA is composed of base pairs of the nucleotides: adenine with thymine, and cytosine with guanine. • The functions of DNA are replication and expression.