1. DNA

2. What is DNA? DNA (Deoxyribonucleic Acid)- is the information of life Achieves its control by determining the structure of proteins The complete instructions for manufacturing all the proteins for an organisms is found on the structure of DNA

3. Structure of Nucleotides DNA is capable of holding all its info because it is a very long molecule DNA is a polymer made of repeating subunits called nucleotides Nucleotides have three parts: 1.Simple sugar 2.Phosphate group 3.A Nitrogenous Base

4. Nucleotides The simple sugar in DNA is called deoxyribose It gives DNA its name- Deoxyribonucleic Acid The phosphate group is composed of one atom of phosphorus surrounded by 4 oxygen atoms

5. COMPONENTS

6. Nitrogenous Bases A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen In DNA, there are 4 possible Nitrogenous bases 1.Adenine (A)2. Guanine (G) 3. Cytosine (C)4. Thymine (T)

7. Nitrogenous Bases Nucleotides join together to form long chains The phosphate groups and sugars form the backbone of the chain; nitrogenous bases stick out like teeth on a zipper Adenine always pairs with thymine: A-T Guanine always pairs with cytosine: G-C

8. Structure of DNA In 1953, James Watson and Francis Crick published a letter in a journal, proposing that DNA is made of two chains of nucleotides held together by nitrogenous bases Hydrogen bonds can form between the nitrogenous bases with holds the two strands together

9. Structure of DNA Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring Because DNA is composed of two strands twisted together, its shape is called a double helix

11. Importance of Nucleotide Sequences All organisms, big or small, are created from the same four nucleotides Their differences result from the sequence of the four different nucleotides along the DNA strands The sequence forms the unique genetic information of an organism

12. Replication of DNA The DNA in the chromosomes is copied in a process called DNA replication During replication, each strand serves as a pattern, or template, to make a new DNA molecule

13. Replication of DNA Replication begins as an enzyme breaks the hydrogen bonds between bases that hold the two strands together, thus unzipping the DNA As the DNA continues to unzip, nucleotides that are floating free in the surrounding medium are attached to their base pair by hydrogen bonds

14. Replication of DNA An additional enzyme bonds these nucleotides into a chain This process continues until the entire molecule has been unzipped and replicated

15. Replication of DNA Each new strand formed is a complement of one of the original, or parent, strands The result is the formation of two DNA molecules, each of which is identical to the original DNA molecule

16. Replication of DNA (Review) 1.Separation of strands 2.Base pairing 3.Bonding of bases 4.Results of replication