DNA, PROTEIN SYNTHESIS, & Mutations

1. DNA, PROTEIN SYNTHESIS, & Mutations Chapters 12 Pages 287-308

2. 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.”

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

5. C. Alfred Hershey & Martha Chase- 1952 Hershey & Chase – determined that DNA transmits genetic information from parent to offspring, & not any other molecule • Worked with bacteriophages – viruses that invade bacterial cells • Usedbacteriophages with radioactive markers (1952)

6. Structure of Bacteriophage • Protein coat – • outer covering • DNA – inner core

7. Hershey & Chase • One bacteriophage had radioactivephosphorus-32in its DNA & was used to infect a bacterial cell • The other had radioactive sulfur-35 in itsprotein coat & was used to infect a bacterial cell • Both bacterial cells were examined • Only the bacteriophage with P-32 was inside the bacterial cell, proving that DNA is the material that transmits genetic info

8. Hershey and Chase

9. 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

10. E. Rosalind Franklin (1952) • Franklin used X-ray diffraction to get information about the structure of DNA • Was able to tell that DNA had an “X” like structure where the strands are twisted around each other • All of these discoveries led to the following….

11. F. Watson and Crick - The discovery of the structure of DNA was made in 1953 by two scientists named James Watson & Francis Crick. - Watson & Crick proposed that DNA is shaped like a “twisted ladder.” - This twisted ladder is also called a “Double Helix.” - They used the findings of the other scientists for their model.

12. Stands for Deoxyribonucleic acid • Functions: 1. Transmit genetic info. to next generation 2. Controls all cell activities, including protein synthesis • DNA A. What is DNA ?

13. B. Structure of DNA - 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)

14. - 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.

16. 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: – – – – – – –

17. Sample Exercise: Strand 1: T – C– A – A – C – G – C – 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

18. Purines vs. Pyrimadines • Adenine and Guanine are PURINES • Thymine and Cytosine are PYRIMIDINES • Remember:

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

20. III. DNA Terminology A. Chromosomes - Tightly compacted strands of DNA found when a cell is dividing! (Needs to be compact to fit in a small space!) - Hold all genetic information. - Chromosomes are passed on to an offspring by its parents. Examples: Fruit Fly = 8 Humans = 46 Shrimp = 254 Chimps = 48 Chicken = 78 Gorilla = 48 Wolf = 78

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

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

23. 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. - This is called a replication fork

24. 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.

25. 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!