AP Biology (An Introduction)

1
Chapter 16
DNA Replication
2
Bell Ringer

• 1. On a sheet of paper
• 2. Write down everything you know about DNA
• -- Who discovered DNA?
• -- What is the structure of DNA?
• -- How does DNA differ from RNA?

3
(No Transcript)
4
The Beginnings

• T. H. Morgans group showed that genes are
  located on chromosomes
• The two components of chromosomesDNA and
  protein were candidates for the genetic material
• The role of DNA in heredity was first discovered
  by studying bacteria and the viruses that infect
  them
• The discovery of the genetic role of DNA began
  with research by Frederick Griffith in 1928

5
Griffin Transformation

• Griffin looked at bacteria mice
• Major finding Transformation
• Killed disease-causing bacteria live, harmless
  bacteria
• Result Live, disease-causing bacteria
• Transformation change in genotype and phenotype
  due to uptake of foreign DNA

6
Mixture of heat-killed S cells and living R
cells
Heat-killed S cells (control)
Living S cells (control)
Living R cells (control)
Living S cells
Healthy Mouse
Healthy Mouse
Mouse dies
Mouse dies
7
Hershey Chase

• What is responsible for transformation?
• Dumb question now, but not so at the time
• Bacteriophages viruses than infect bacteria
• Consist of protein DNA
• Which is the transformative agent?

8
EXPERIMENT
Radioactive protein
Phage
Bacterial cell
DNA
Batch 1 radioactive sulfur (35S)
Radioactive DNA
Batch 2 radioactive phosphorus (32P)
9
EXPERIMENT
Empty protein shell
Radioactive protein
Phage
Bacterial cell
DNA
Batch 1 radioactive sulfur (35S)
Phage DNA
Radioactive DNA
Batch 2 radioactive phosphorus (32P)
10
EXPERIMENT
Empty protein shell
Radioactivity (phage protein)
in liquid
Radioactive protein
Phage
Bacterial cell
DNA
Batch 1 radioactive sulfur (35S)
Phage DNA
Centrifuge
Pellet (bacterial cells and contents)
Radioactive DNA
Batch 2 radioactive phosphorus (32P)
Centrifuge
Radioactivity (phage DNA) in pellet
Pellet
11
Chargaffs Rules

• In DNA
• A T G C
• Why would this be true?

12
(No Transcript)
13
Structural Model of DNA?

• M. Wilkins R. Franklin use X-ray
  crystallography to study molecular structure
• Watson Crick deduced that DNA was 2-stranded
• Double Helix

14
DNA Replication

• DNA ? DNA
• 2 strands separate, and each one is paired using
  complementary bases

15
Themes (meh.)

• Science as a process
• Regulation
• Interdependence in nature
• Science, Technology, Society

16
Semiconservative Replication

• Each daughter molecule 1 old strand (Conserved
  from parent strand) 1 newly replicated strand
• Called Semiconservative
• Half of the strands are conserved from the parent
• Competing (Incorrect models) Conservative
  Dispersive

17
(No Transcript)
18
DNA Replication

• 16_05DNAandRNAStructure
• 16_07DNADoubleHelix
• 16_09Overview

19
(No Transcript)
20
(No Transcript)
21
Telomeres

• Eukaryotic chromosomal DNA molecules have at
  their ends nucleotide sequences called telomeres
• Telomeres do not prevent the shortening of DNA
  molecules, but they do postpone the erosion of
  genes near the ends of DNA molecules
• It has been proposed that the shortening of
  telomeres is connected to aging
• Telomerase enzyme that lengthens the telomere
• Telomerase in cancerous cells?

22
(No Transcript)
23
(No Transcript)
24
PROKARYOTE
EUKARYOTE