BIOL
211-CELLULAR AND ORGANISMAL BIOLOGY
Lecture
Outline for
Topic: discovery of DNA as
the hereditary material
Chapter 2 – review DNA
structure from section 2.3, Chapter12 sec 12.1, 12.2
Figures used in lecture: 12.2, 12.3, 12.7, 12.8, 12.9, 12.10
Additional resources
The DNA molecule is shaped like a twisted ladder.
Click on "Animation" and Watson and Crick will explain DNA structure
to you.
Watson and Crick - a discussion of their work
Discovery of DNA as the Genetic Material – Avery
and mice, Chargaff, Watson & Crick
NOTE: This material is
review. We discussed this in lecture on
Define: nucleic acids, DNA,
RNA, nucleotide, nitrogenous base, adenine (A), thymine (T), cytosine (C),
guanine (G), uracil (U)
You should be able to:
1. Describe the structure of a nucleotide
2. Distinguish between a DNA nucleotide and a
RNA nucleotide based on the structure of the sugar and the difference in the
nitrogenous bases that are used in DNA and RNA
3. Describe the structure of the double helix
Early in the last century,
scientists proposed that the genetic material was carried on the
chromosomes. Because chromosomes are
composed of both DNA and protein, they did not know whether DNA or
protein was carrying the genetic information.. A few experiments were done that confirmed
that DNA is the genetic material. These
experiments include:
1. Frederick Griffith, 1920’s
2. Avery, MacLeod, McCarty, 1944
Define: Streptococcus pneumoniae, RNAse, DNAse, virulent, avirulent,
transforming principle
You should be able to
1. Describe the experiments performed by
- exactly how
they performed their experiment
- the results of
the experiment
- the conclusion
that was drawn from the results
Define: "Chargaff's
Rules", X-ray crystallography,
Scientists believed that
discovering the structure of DNA would hopefully reveal how DNA performs its
functions. Clues to the structure of DNA
came from several labs:
1. Erwin Chargaff,
1950
2. Rosalind Franklin and Maurice Wilkins, early
1950’s
3. James Watson and Francis Crick, 1953
You should be able to
1. Understand the research performed by each of
the scientists listed above and how their research contributed to determining
the structure of DNA
2. Be able to identify
which nitrogenous bases are purines and which are pyrimidines based on their
general structures.
2. Explain why a purine must form a
complementary base-pair with a pyrimidine,
Define: deoxyribose, nitrogenous base, purine,
pyrimidine, sugar-phosphate backbone, hydrogen bonding, complimentary base
pairing, antiparallel, 5' end, 3'end, helix, double helix
Today’s Lecture (
DNA Topics we will cover:
1. DNA is the hereditary material.
2. DNA Structure
3. DNA Function
a. DNA Replication
b. DNA controls protein synthesis
1) transcription 2) translation
Nucleic Acids
nucleotide structure:
comparison of DNA to RNA:
Early 1900’s
A primary question was “Is
the DNA or the protein carrying the genetic information?”
Frederick Griffith, 1920’s
- Streptococcus pneumoniae
S strain (smooth) – virulent; R strain (rough) - avirulent
-investigating why only S
strain causes pneumonia
-method of experiment:
Avery, MacLeod, McCarty 1944
-method of experiment:
Avery, MacLeod, McCarty”s conclusion:
Erwin Chargaff,
1950
-“Chargaff’s Rules”;
Rosalind Franklin, Maurice
Wilkins
- early
1950’s
- X-ray crystallography
James Watson, Francis
Crick 1953
-method of experiment:
Watson and Crick’s
conclusion: