Unit 6 – DNA Structure and Replication Chapter 8, Sections 2 & 3 New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 DNA Structure New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: The Molecule of Heredity Objective: You will be able to describe the molecule of DNA New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: the “Base”ics DNA – Deoxyribonucleic Acid Unit of heredity in all living things Contains the information for making proteins Only in NUCLEUS Made up of nucleotides New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 DNA: The “Base”ics Nucleotide Sugar (Deoxyribose) Phosphate Nitrogen Base New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: The “Base”ics Four Nitrogen Bases (DNA) Adenine (A) Thymine (T) Cytosine (C) Guanine (G) New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: the “Base”ics Adenine & Guanine = Purines Cytosine & Thymine = Pyrimidines Hint to remember…Look at the “Y”s !! New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: the “Base”ics Chains are formed by joining the sugar of one nucleotide to the phosphate of the next. “Sugar – Phosphate Backbone”

DNA: the “Base”ics Nitrogen bases come off of the sugar (deoxyribose) Hydrogen bonds hold the bases together to form a pair A always pairs with T C always pairs with G Called complementary bases Hydrogen Bonds Hydrogen Bonds New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: the “Base”ics Chargaff – 1950 amount of A always EQUALS amount of T amount of G always EQUALS amount of C Determined that A bonds to T and C bonds to G in the structure of DNA Called the Chargaff rules or the base pairing rules New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Learning Check What is the name for DNA? What information does DNA hold? What are the monomers for DNA? What are the 3 parts of a nucleotide? What are the 4 bases in DNA? What are the base pairing rules? What holds the bases together in a DNA molecule? New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Learning Check What is the complimentary strand of DNA? 5’ –ATCGCG -3’ New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA: the “Base”ics Wilkins & Franklin – 1953 used x-ray diffraction of DNA; found DNA helical What type of helix was unclear…

DNA: the “Base”ics Watson & Crick (1953)– determined 3D “Double Helix” structure of DNA (twisted ladder)

New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA and Nucleotide Sequences All organisms have DNA All DNA is made of the same bases(4 different nucleotides) How are we different from dogs, cats, trees, etc? Different organisms are composed of different proteins New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA and Nucleotide Sequences The different ways the nucleotides (A,T,G,C) are arranged create different proteins The order of nucleotides (ATCG) in each gene has the info to make a string of amino acids which make a specific protein Just think…. Ant vs. Tan (same letters but very different things) The sequence of nucleotides carries different genetic information A-T-T-G-A-C vs. T-C-C-G-A-A The closer related organisms are the more similar their DNA sequences New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA sequence Nucleotide sequence of chimp is similar to gorilla, but very different from a rose. We can use nucleotide sequence to determine evolutionary relationships among organisms. Can use nucleotide sequence to determine if 2 people are related or identify criminals. New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Learning Check What is the structure of DNA? How is DNA organized? Why are we different from other organisms and other people? New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Closing On the back of the sheet I just handed you, write the complementary strand of DNA for the following DNA sequence: 5’- TCGAAATCTACCGGTA- 3’ State Standard 4.1, 4.2, and 4.3

Replication New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Replication Objective: You will be able to explain replication and create a new strand of DNA through replication. New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA Replication DNA Replication – process of copying DNA Occurs every time a cell reproduces in mitosis or meiosis Occurs in the S phase of interphase in the cell cycle Replication assures that every cell has a complete set of identical genetic info Semi-conservative process - produces 2 copies that each contain one of the original strands and one entirely new strand New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

State Standard 4.1, 4.2, and 4.3

DNA is used as a “template” New strand is called a compliment New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Steps of replication Enzyme helicase breaks the weak hydrogen bonds at origins of replication between nitrogen base pairs and “unzips” the DNA strand Happens at more than one origin of replication on DNA Free nitrogen bases in nucleus join with the open DNA strand with the help of DNA polymerase DNA polymerase – enzyme that bonds the nitrogen bases together Two new strands of DNA are made New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

DNA Replication Replication is very fast Replication is very accurate In humans, about 50 nucleotides every second at each replication origin Replication is very accurate Only about 1 error in 1 billion nucleotides It has a built in “proofreading” function DNA polymerase can detect errors and replace incorrect nucleotides New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Learning Check What is DNA replication? When does DNA replication happen? Why does DNA replication happen? What “unzips” the DNA molecule in replication? What molecule helps bond the new nucleotides to the DNA template? New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3

Learning Check Make two daughter strands of DNA from the parent DNA below. Label template and daughter strands. Circle the TWO daughter DNA molecules. A-T T-A C-G G-C New State Standards: H.B.2A.1 ; H.B.4A.1 ; H.B.4A.2 SC: Science (2005), SC: Grades 9-12, HS: Biology Standards B-4.1; B-4.2 and B-4.3