1. AP Bio: Tuesday, 1/31/12 Unit 8: Molecular Genetics
Homework:
Finish Molecular Genetics Review Packet Part A
Problem Set 12 #1
Do Now:
Look over your midterm exam.
Read the intro of the Molecular Genetics review packet and complete as much of Part A as you can

2. AP Bio: Tuesday, 2.1.11 Unit 8: Molecular Genetics
Homework:
Finish Molecular Genetics Review Packet Part A
Problem Set 12 #1
Goals for Today:
Interpret the results of historical experiments in molecular genetics
Describe the structure of DNA
Agenda:
Review Midterm Exams
Lecture: Historical Experiments with DNA
Exam Scores:
100-90
89-80
79-70
69-60
59-0 2 6

3. A History of Experiments in Molecular Genetics
Important questions of the 20th century:
What is the genetic material?
What is its structure?
How does it replicate?

4. Griffith’s classic experiment
Britain, 1928

5. Griffith’s conclusions
Live, nonpathogenic bacteria have taken up some chemical from the dead, pathogenic bacteria (transformation)
The offspring of the nonpathogenic bacteria inherited this material, becoming pathogenic
Next question: What is the transforming material?

6. What is the genetic material? Previous studies have revealed:
Genes are on chromosomes
Chromosomes are passed from one generation of cells to the next during cell division
Chromosomes are made of proteins and nucleic acids
Therefore, the genetic material could be
Protein
DNA
RNA
Whatever this material is, it must be able to
Store genetic info
Replicate

7. AP Bio: Wednesday, 2/1/12 Unit 8: Molecular Genetics
Homework:
Problem Set 12 #1, 2, 3
Do Now: (to think about, not necessarily write down)
What is the difference between replication and transcription?
Take out your notes… What was the major conclusion from Avery, McCarty, and McLeod’s experiment?
Goals for Today:
Interpret the results of historical experiments in molecular genetics
Describe the structure of DNA
Explain the major steps and enzymes involved in DNA replication

8. Avery, McCarty, McLeod United States, 1944 What is the genetic material of bacteria?
Conclusion ?

9. Hershey & Chase 1952 What is the genetic material of viruses?
Background:
Bacteriophage (“phage”) are viruses that infect bacteria & re-program the bacteria cell to make more viruses
Phage are made of
Protein shell -- DNA (or RNA) inside
Hypothesis:
If protein is the genetic material, then bacteria infected with phage containing radioactive protein will become radioactive
If DNA is the genetic material, then bacteria infected with phage containing radioactive DNA will become radioactive

10. Hershey & Chase 1952
Conclusion?

11. Early 1950s: DNA is genetic material
Evidence:
Bacteria: Avery, McCarty, MacLeod
Viruses: Hershey & Chase
Eukaryotes:
DNA (but not protein) content of cells doubles exactly during mitosis
DNA (but not protein) content of diploid cells is exactly double that of haploid cells
Next question:
What is the structure of DNA?

12. We already know (1950) We don’t know: DNA is a polymer of nucleotides
Each nucleotide has three parts:
Pentose sugar (deoxyribose)
Phosphate group
Nitrogenous base (4 types)
Adenine Cytosine
Guanine Thymine
We don’t know:
What is the polymer structure?
How does DNA encode complex genetic info?
How does its structure enable replication?

13. 4 Nitrogenous Bases
PYRIMIDINES PURINES
Sugar
Sugar
Sugar
Sugar

15. What was Watson & Crick’s evidence??
Erwin Chargaff (1947)
Percentage of DNA bases (A, G, T, C) varies between species
But always %A = %T and %G = %C
Rosalind Franklin (1952)
Made an X-ray diffraction
image of DNA that
suggested a double helix

16. The Breakthrough: Watson & Crick 1953
DNA is a double-stranded polymer
A H-bonds w/ T
C H-bonds w/ G
Biochemical reasons (width, H-bonding)

17. DNA molecules twist to form a DOUBLE HELIX

18. Next question: How does DNA replicate?
A quote from Watson & Crick’s Nobel Prize-winning paper:
“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” (1953)

19. 3 Hypotheses for DNA Replication

20. Meselson-Stahl experiment
Parent DNA molecules are “heavy”
Newly-synthesized DNA molecules are “light”
1st round of replication
2nd round of replication

21. Meselson-Stahl Conclusion:
DNA replication is semi-conservative.

22. DNA Structure

23. AP Bio: Thursday, 2/2/12 DNA Replication & DNA Technologies
Homework:
Problem Set deadline extended until next Tuesday
Tomorrow’s classwork (pre-lab and worksheet) also due Tuesday if you don’t finish in class
Do Now:
What is the difference between DNA replication and making RNA (transcription)?
From your review packet, what are 3 major steps of DNA replication?
From yesterday’s notes, what are 3 enzymes important in starting the process of DNA replication?

24. AP Bio: Thursday, 2/2/12 DNA Replication & DNA Technologies
Goals for Today:
Explain the major steps and enzymes involved in DNA replication
Explain how scientists use knowledge of DNA structure and replication to study and manipulate DNA:
How can we…
Separate pieces of DNA based on their size
Cut DNA at specific places
Make many copies of a specific gene
Find out the sequence of a DNA strand
Attach different pieces of DNA (possibly from different species) together in order to genetically engineer an organism

25. DNA Replication: Key enzymes in starting the process

26. DNA Replication: Elongation

27. DNA Replication: Leading vs. Lagging Strands

28. Lagging Strand
Elongation

29. DNA Replication: Summary of Key Molecules
Helicase – Splits apart the template DNA strands (unwinds and unzips)
RNA Primer – short strand of RNA on daughter strand that DNA Pol uses to get started
DNA Polymerase – assembles nucleotides on daughter strand (complementary to template strand)
Leading strand – daughter strand that is synthesized continuously
Lagging strand – daughter strand that is synthesized dis-continuously
Okazaki fragment – pieces of lagging strand that need to be connected
DNA Ligase – enzyme that connects fragments of DNA together

30. DNA Tools & Technologies
DNA Sequencing
Adel
Fatima
Kimberly
Aaron
PCR
Imad
Klara
Drishti
Nicole
Restriction Enzymes
Christina
Poppy
Kira
Djinnie
Research your technology in the textbook
Summarize on the handout. Use bullet points no longer than 2 lines each! The goal is to SUMMARIZE with the ESSENTIAL info!
Create a powerpoint or a Word doc (template on AP Bio blog)
Also be ready to DRAW a simple picture on the board
Gel Electrophoresis
Rishab
Nehemie
Jasmine
Talia