DNA & PROTEIN SYNTHESIS Chapters 12 & 13, Pages 287-333

Chapter 12: Section 1 I. History A. Frederick Griffith- 1928 - Tried to figure out how bacteria made people sick? - Heat killed, disease-causing bacteria passed “something” along to harmless bacteria. - He called this process “Transformation.”

- Determined DNA is the molecule of inheritance and not proteins. B. Avery- 1944 - Determined DNA is the molecule of inheritance and not proteins. Did this by destroying other cell parts piece by piece.

- Studied viruses, non-living particles that contain DNA. C. Hershey & Chase- 1952 - Studied viruses, non-living particles that contain DNA. - Discovered that DNA is the genetic material responsible for transformation. Click for animation!

D. Erwin Chargaff- Late 1940’s Found there are 4 bases in a DNA molecule Adenine, Guanine, Cytosine and Thymine Found that the amount of A = T and G = C Chargaff warned that “the technology of genetic engineering poses a greater threat to the world than the advent of nuclear technology. An irreversible attack on the biosphere is something so unheard of, so unthinkable to previous generations, that I only wish that mine had not been guilty of”

II. DNA (DeoxyRibo Nucleic Acid) A. Discovery of Structure - The discovery of the structure of DNA was made in 1953 by two scientists named Watson & Crick. - Watson & Crick proposed that DNA is shaped like a “twisted ladder.” - This twisted ladder is also called a “Double Helix.”

What about Rosalind Franklin? Watson and Crick used the data from Rosalind Franklin and Maurice Wilkins X-ray Crystallography to determine the structure. Watson, Crick and Wilkins shared the Nobel prize, Franklin was robbed!! Rosalind Franklin song

B. What is DNA made of? - DNA is made of nucleotides. 1. Nucleotides consist of the following: a. Deoxyribose – a sugar b. A Phosphate Group c. A Nitrogen Base 1. Four possibilities a. Adenine (A) b. Guanine (G) c. Cytosine (C) d. Thymine (T)

Nucleotide

- These nucleotide bases join together to form a long single strand. - Each long single strand of nucleotides connects to “another” single strand of nucleotides. - The two strands are held together by hydrogen bonds.

C. Base Pairing Rules 1. Adenine always pairs with Thymine. 2. Cytosine always pairs with Guanine. - The different order of these bases is what makes organisms different. Example: Strand 1: A – G – T – T – C – T – A – G Strand 2: T – C – A – A – G – A – T – C Sample Exercise: Strand 1: C – G – A – T – G – T – A – C Strand 2: – – – – – – –

Sample Exercise: Strand 1: C – G – A – T – G – T – A – C Strand 2: – – – – – – – - The more closely related two organisms are the more alike the order of their nucleotides in their DNA will be. Example: Humans  Chimps Gorillas Orangutans

Purines vs. Pyrimadines Adenine and Guanine are PURINES Thymine and Cytosine are PYRIMIDINES

Purines and Pyrimidines Purines can only pair with pyrimidines due to their size and shape.

III. DNA Terminology A. Chromosomes - Tightly compacted strands of DNA found when a cell is dividing! - Hold all genetic information. - Chromosomes are passed on to an offspring by its parents. Examples: Humans = 46 Shrimp = 254 Chimps = 48 Chicken = 78 Gorilla = 48 Wolf = 78

B. Chromatin - When a cell is not dividing, DNA is in the form of chromatin. - Loosely packed DNA that is wrapped around proteins.

C. Genes - A section of DNA on a chromosome that codes for a specific protein.

IV. DNA Replication SECTION 2 A. DNA is copied before a cell divides so that each new cell has it’s own genetic copy. B. There are 4 main steps: STEP 1: - DNA is unzipped by the enzyme HELICASE and now two single strands begin to unwind. - Hydrogen bonds are broken.

STEP 2: - Each unwound strand of DNA acts as a template to produce two new strands of DNA. STEP 3: - An enzyme named DNA Polymerase will read each unwound strand and join new complimentary nucleotides to each.

- This occurs until the whole strand is replicated. STEP 4: - This occurs until the whole strand is replicated. - Now there are two identical DNA molecules. - Each strand contains one original and one complimentary strand. Click image for animation!