1928 Frederick Griffith 1944 Oswald Avery - repeated Griffith’s experiment Proves DNA stores and transmits information

1952 Alfred Hershey and Martha Chase Proved that DNA contained genes and found in all cells.

In science it is understood that DNA codes for proteins that are needed for organisms to survive. DNA is the fundamental molecule of every living thing on Earth. DNA RNA Protein TranscriptionTranslation

DNA must store, copy and transmit information in a cell! Storing - most important job; codes for genes Copying - replication before division to ensures each new cell has complete set of genes Transmit - stored information must be carefully passed on to offspring

DNA is short for Deoxyribonucleic Acid DNA contains information for life and is a polymer made of repeating nucleotides (monomers).

Nitrogen base = carbon ring structure that contains nitrogen 4 Possible: 1.Adenine (A) 2.Guanine (G) 3.Cytosine (C 4.Thymine (T) * A-T always pair while C-G will always pair!!

Nucleotide = phosphate group, 5- carbon sugar ribose, and nitrogen base.

* Adenine (A) and Guanine (G) belong to a group of chemicals called purines while Cytosine and Thymine belong to a group of chemicals called the pyrimidines.

- Phosphate and deoxyribose create a covalently bonded backbone. (Phosphodiester Bond)

-rules of base composition 1.The total amount of pyrimidine nucleotides (T + C) always equals the total amount of purine nucleotides (A + G) 2. The amount of T always equals A, and the amount of C always equals the amount of G. But the amount of A + T is not necessarily equal to the amount of G + C.

* 3.4 billion base pairs in humans!!!

Using the work of Rosalind Franklin and her X-ray diffraction photograph. James Watson and Francis Crick were able to conclude the final structure of DNA as a double helix in Photo 51

* The discovery of the DNA structure was monumental to the scientific world. * Watson and Crick saw that the strands of DNA ran “antiparallel” to each other in a 5’ to 3’ direction.

Since DNA is double stranded. The double helix structure can be described as a “twisted ladder”. The sides of the ladder are made up of repeating phosphates and sugars while the rungs contain the nitrogen bases linked together by hydrogen bonds.

* Sequence forms unique genetic information of organism. Nucleotiede sequence can be in any order. Ex. A-T-T-C-G-C differs from A-T-T-G-T-C - Forms the genetic code!!! Each sequence responsible for a unique protein

* Before cells divide, copies of chromosomes must be made to ensure that the new cells have the same number of chromosomes. * DNA Replication = process of DNA in chromosomes duplicating. * Takes place in nucleus of cell! Has 4 steps…

1.Separation of Strands -DNA helicase enzyme breaks down the hydrogen bonds between nucleotides and DNA “unzips” exposing the nucleotides. 2. Base Pairing - free nucleotides base pair (A-T, C-G) to exposed nucleotides via DNA polymerase. New strands created 5’ to 3’.

3. Bonding of Bases - sugar and phosphate parts of adjacent nucleotides bond to form backbone of new strand. Done by DNA ligase. 4. Results of Replication -product is two molecules of DNA from one original strand. -Semi- conservative.

Replication video Okazaki Fragment

* Multiple replication forks allow for faster replication of DNA!! (Eukaryotes only)