2 DNA Consists of Nucleotides Sugar Phosphate backbone:Deoxyribose sugar (Ribose sugar in RNA)Phosphate GroupNitrogenous Base (4 types):Adenine, Thymine, Guanine, and Cytosine.Purines: Adenine and GuaninePyrimidines: Thymine and Cytosine
3 What is DNA’s form? Double helix- Looks like a spiral stair case. Sugar phosphate backbone never changes, so what part of DNA changes from organism to organism?Nitrogenous Base order: what causes all of life’s diversity.
4 Building a DNA Model First thing: Color all the like pieces the same color.So this means that all the adenine is the same color, guanine is a different color, etc.Then cut out your pieces and prepare for assembly.
5 DNA STRUCTURE CONNECTED WITH STRONG BONDS WHAT ARE THE PARTS OF A NUCLEOTIDE?CONNECTED WITH STRONG BONDSSUGARPHOSPHATEBASEThese are covalent bonds.
6 DNA STRUCTURE CONNECTED WITH WEAK BONDS (dotted line) These are called hydrogen bonds.
7 DNA STRUCTUREHow many bases?How many base pairs?
10 DNA LOOKS LIKE A LADDER SUGAR-PHOSPHATE BACKBONE BASES: ADENINE THYMINECYTOSINEGUANINE
11 Base Pairing Hydrogen bonds connect particular base pairs. Adenine bonds with Thymine (A=T)Guanine bonds with Cytosine (G=C)So purines bond to pyrimidinesLabel the DNA strandDeoxyribose SugarPhosphate GroupNitrogenous BasesAdenineThymineGuanineCytosinePurinesPyrimidines
12 How many C’s?How many G’s?How many A’s?How many T’s?
13 If they bond together they must be in equal percentages. Q: If there is 30% Thymine and 20% Cytosine, how much Guanine and Adenine is there?A: 20% GuanineA: 30% Adenine
14 If we know 1 percentage can we determine the rest? If there is 14% Adenine, what percent Thymine will there be?Thymine= 14%What percent Guanine and Cytosine?Total 100% - (A%+T%) = (C%+G%)100% - 28% = 72%(G+C)72%/2 = 36%G and 36%C
15 Sample QuestionIf the is 28% Guanine, what percent Adenine, Thymine, and Cytosine will there be?Find Cytosine first (if BP’s with Guanine)Cytosine = 28%100% - (28%+28%) = 100% - (56%)= 44%44%/2 = 22%A and 22%T
16 DNA Replication Follow along and fill in the blanks during this video.
17 DNA Replication Helicase is the enzyme that unwinds DNA. The parent DNA is used as a template.DNA polymerase is used to connect complimentary base pairs to the template strand.New nucleotides join together to make semiconservative DNA.
18 Meselson-Stahl: Semiconservative Replication Semi: Like a semicircle. What does it mean?Conservative: To conserve (like the environment). What does it mean?Why is DNA replication called this?