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2 DNA DNA.DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell.

3 DNA Why do we study DNA? We study DNA for many reasons, e.g., its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops.

4 Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA.

5 The Shape of the Molecule DNA is a very long polymer. The basic shape is like a twisted ladder or zipper. This is called a double helix.

6 The Double Helix Molecule The DNA double helix has two strands twisted together.

7 Nucleotides CC C O Phosphate O C C O -P O O O O O O O One deoxyribose together with its phosphate and base make a nucleotide. Nitrogenous base Deoxyribose

8 One Strand of DNA The backbone of the molecule is alternating phosphates and deoxyribose sugar The teeth are nitrogenous bases. phosphate deoxyribose bases

9 One Strand of DNA One strand of DNA is a polymer of nucleotides. One strand of DNA has many millions of nucleotides. nucleotide

10 Four nitrogenous bases Cytosine C Thymine T Adenine A Guanine G DNA has four different bases:

11 Two Kinds of Bases in DNA Pyrimidines are single ring bases.Pyrimidines are single ring bases. –T, C Purines are double ring bases.Purines are double ring bases. –A, G C C C C N N O N C C C C N N N N N C

12 Thymine and Cytosine are pyrimidines Thymine and cytosine each have one ring of carbon and nitrogen atoms.Thymine and cytosine each have one ring of carbon and nitrogen atoms. C C C C N N O N cytosine C C C C N N O O thymine C

13 Adenine and Guanine are purines Adenine and guanine each have two rings of carbon and nitrogen atoms.Adenine and guanine each have two rings of carbon and nitrogen atoms. C C C C N N N Adenine N N C C C C C N N O N Guanine N N C

14 Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. The teeth are the nitrogenous bases but why do they stick together?

15 C C C C N N O N C C C C N N O N N N C Hydrogen Bonds The bases attract each other because of hydrogen bonds. H bonds are weak by themselves, but collectively they can be strong. (millions in DNA) The bonds between cytosine and guanine are shown here with dotted lines

16 Hydrogen Bonds, Hydrogen Bonds, cont. When making hydrogen bonds, cytosine always pairs up with guanine Adenine always pairs up with thymine Adenine is bonded to thymine here C C C C N N N N N C C C C C N N O O C

17 Complimentary base-pairs 2 simple rules: Adenine and Thymine always bond together A T Cytosine and Guanine always bond together C G

18 DNA by the Numbers Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only m. The earth is 150 billion m or 93 million miles from the sun.

19 Double Helix History Watson and Crick won the 1962 Nobel Prize for the structure of the double helix. –Used other’s research and x rays.

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21 * All cells have the same DNA in an organism. Other factors determine which genes are used

22 Replication is when two nucleotide chains separate, unwind, and then become templates for new chains

23 Replication Fork is where replication begins on the DNA strand

24 Helicase is the enzyme that breaks the H bond and creates two DNA templates

25 DNA polymerase binds to the DNA chains and forms new chains with nucleotides from the surrounding cytoplasm

26 More than one DNA polymerase binds to the chains all throughout the DNA to speed up the process. Example: Fruit Flies

27 The complementary nature of the nucleotides gives a more accuracy replication of DNA.

28 II. Accuracy and Repair

29 1 mistakes occur in replication per nucleotides.

30 B. Mutationis change in the nucleotide sequence. C. Proofreaders- follow throughout chain and check over the DNA polymerase work 1. Accuracy increases to 1 out of 1 Billion nucleotides.

31 D. Environmental Damage 1. UV light can cause mutations and damage genes 2. Foreign chemicals introduced to the cell can also damage the chain.

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