AP Bio: Tuesday, 1/31/12 Unit 8: Molecular Genetics

1
AP Bio Tuesday, 1/31/12Unit 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, 2.1.11Unit 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 6 2 0
3
A History of Experiments inMolecular Genetics

• Important questions of the 20th century
• What is the genetic material?
• What is its structure?
• How does it replicate?

4
Griffiths classic experiment

• Britain, 1928

5
Griffiths 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, 2/1/12Unit 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 McLeods
  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, McLeodUnited States, 1944What
is the genetic material of bacteria?
Conclusion ?
9
Hershey Chase1952What 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 Chase1952
Conclusion?
11
Early 1950s DNA is geneticmaterial

• 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)

• 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 dont 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
14
(No Transcript)
15
What was Watson Cricks 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
TheBreakthroughWatson Crick1953

• 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 questionHow does DNA replicate?

• A quote from Watson Cricks 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, 2/2/12DNA Replication DNA
Technologies

• Homework
• Problem Set deadline extended until next Tuesday
• Tomorrows classwork (pre-lab and worksheet) also
  due Tuesday if you dont 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 yesterdays notes, what are 3 enzymes
  important in starting the process of DNA
  replication?

24
AP Bio Thursday, 2/2/12DNA 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 ReplicationKey enzymes in starting the
process
26
DNA ReplicationElongation
27
DNA ReplicationLeading vs. Lagging Strands
28
Lagging Strand Elongation
29
DNA ReplicationSummary 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
Restriction Enzymes Christina Poppy Kira Djinnie
PCR Imad Klara Drishti Nicole
DNA Sequencing Adel Fatima Kimberly Aaron

1. Research your technology in the textbook
2. Summarize on the handout. Use bullet points no
   longer than 2 lines each! The goal is to
   SUMMARIZE with the ESSENTIAL info!
3. Create a powerpoint or a Word doc (template on AP
   Bio blog)
4. Also be ready to DRAW a simple picture on the
   board

Gel Electrophoresis Rishab Nehemie Jasmine Talia