1. DNA: The Genetic Material
Chapter 9
DNA: The Genetic Material

2. Identifying The Genetic Material
What is your genetic information made of? Proteins or DNA
Griffith’s work
Discovery of “Transformation” or a change in the genes by taking in foreign information
Avery’s work
Demonstrated that DNA contains the genetic information
Hershey and Chase’s work
Used bacteria to prove DNA is where the genetic information is, not proteins.

3. The structure of DNA
Watson and Crick receive credit for creating the first DNA model
Double helix: two strands twisted around each other, like a winding stair case.
Each strand is linked nucleotides which is made up of 3 parts.
Phosphate group, five carbon sugar, and a nitrogen base
Five carbon sugar is called deoxyribose (hence DNA= deoxyribonucleic acid)
Nitrogen bases:
Purines: 2 ringed molecules; Adenine and Guanine
Pyrimidines: single ringed molecules; thymine and cytosine

4. Used all of the above in development of their model
Chargaff’s observations:
The amount of adenine always equals the amount of Thymine
The amount of guanine always equals the amount of Cytosine
Wilkins and Franklin
Used X-ray diffraction to study the structure of DNA
Successfully imaged a DNA
Watson and Crick (again)
Used all of the above in development of their model
Determined base-pairing rules:
Purine always matches to a pyrimidine
Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds
Cytosine (C) pairs with Guanine (G) via 3 hydrogen bonds
Termed complementary base pairs

6. So therefore, complimentary base pair rules:G- C-

7. DNA Replication: the process of making a “new” strand of DNA (occurs during the S phase)
Steps:
DNA unwinds (DNA helicases are the enzymes responsible for this), other enzymes hold them apart, at replication forks.
DNA polymerases attach at replication forks adding new nitrogen bases to the exposed base
Upon completion, DNA polymerase detaches, two new strands are present, each being part new and part of the old strand.

9. Genes to Protein (this is found in chapter 10)
RNA (ribonucleic Acid) single strand, made from the genetic information found on DNA
NO THYMINE, instead thymine is replaced with Uracil (which is a pyrimidine)
Two main stages in creating proteins, transcription and translation.
Transcription: info is transferred from DNA to an RNA.
Steps:
RNA polymerase binds to a specific spot on the DNA (the “start” spot)
Unwinds a specific area of DNA
RNA polymerase adds and links complimentary RNA nucleotides as it “reads” the DNA
Continues until it reaches the “stop” spot
New strand that is created is modified and becomes mRNA (“messenger” RNA)

10. The Genetic Code (the three letter words)
Codons: are three letter words, sequences, that “code” for information on the RNA
All are listed below, and no you don’t have to memorize it. I will give to you. BUT you should be able to read it.

11. Translation: the synthesis of the proteins.
Steps:
mRNA leaves nucleus and travels (in the cytoplasm) to a Ribosome
There it joins the ribosome, and it starts to read the mRNA
In the ribosome, reading begins with “start codon” at the P site
Transfers to the A site and continues
tRNA (or transfer RNA) has anti codons (or opposite of the codon found on the mRNA) which as a specific amino acid attached to it.
The amino acids are joined together, forming the protein.