Title: Nucleic Acids
Introduction: Most biologists were now convinced that DNA was the genetic
material. However, they still did not know what specific arrangements gave DNA its
unique properties. How is it capable of storing, copying and transferring
information onto succeeding generations. How does its structure account for its role
in heredity?
1- The building blocks of DNA
a- The heritable genetic information of an organism is stored in a molecule
called DNA (deoxyribonucleic acid)
b-
c- RNA (ribonucleic acid) also plays a role in the functioning of cells
d1- Only four types of nucleic acids make up DNA, each contain
a- A deoxyribose sugar
b- A phosphate group
c- a nucleotide held to another nucleotide by a hydrogen bond
1- The 4 base pairs are adenine, thymine, quinine and cytosine
2- Adenine always bonds with Thymine and guanine always
bonds with cytosine
d-The DNA Strands
1- are composed of a deoxyribose sugar and phosphate and a
nucleotide
2- This repeating set of units is called the sugar-phosphate
backbone
3- The nucleic acids are inside (make up the rungs of the
ladder) held together by hydrogen bonds
4- Adenine and guanine are purines (they have a double ring)
and thymine and cytosine are pyrimidines (they have a single
ring)
e- DNA Structure
1- In the early 1950’s Rosalind Franklin and Maurice Wilkens using
X-ray crystallography provided a collection of photographs of
DNA. These pictures gave clues to the shape and dimensions of
complex molecules. These photos showed the basic shape of DNA
to be a helix.
2- The Double Helix
a- Watson and Crick working with Maurice Wilkens and Rosalind
Franklin at the Cavendish Labs at Cambridge University
discover the double helix structure of DNA
b- They could not have done it without analyzing the x-rays of
Rosalind Franklin – The double helix is important because it
provides the necessary template for DNA replication
3- Complimentary base pairing
a- Based on the double helix model, Watson and Crick concluded
that the base pairs had to align in very specific ways
b- A goes with T, G goes with C
c- Complimentary base pairing allows for two identical daughter
strands of DNA to be made (with the help of helicase and DNA
polymerase) and divide into each of the two daughter cells during
mitosis
d- In 1953 Watson and Crick published their work in the journal
Nature Few milestones in the history of biology have been as
important as the discovery of the double helix structure of DNA
and complimentary base pairing. With the help of the famous
“Photo 51” Watson, Crick and Wilkens received the Nobel prize for
their work for Medicine in 1962.