Powerpoint Presentation: The Nucleic Acids
Molecular Genetics Index
The Chemical Nature if the Gene
Ribonucleic Acid (RNA)
The Characteristics of the Genetic Code
The Genetic Code
The lac Operon
Topic Chapters Index
By brian0918 (Own work) [Public domain],
via Wikimedia Commons
The DNA is made from two strands of polynucleotide
The sister strands of the DNA molecule run in opposite directions (antiparallel).
They are joined by the bases.
Each base is paired with a specific partner
A is always paired with T
C is always paired with G
This the sister strands are complementary but
The bases are joined by hydrogen bonds, individually weak but collectively strong.
The Nucleic Acids
First isolated by Friedrich Miescher in 1869.
He isolated what he called nuclein from the nuclei of pus cells.
Nuclein was shown to have acidic properties, hence it became called
Two types of nucleic acid are found
The distribution of nucleic acids in the eukaryotic cell is interesting
DNA is found in the nucleus with small amounts in mitochondria and chloroplasts.
found throughout the cell.
DNA as genetic material: The circumstantial evidence
It is present in all cells and virtually restricted to the nucleus.
The amount of DNA in somatic cells (body cells) of any given species is constant (like the
number of chromosomes). The RNA content varies a lot.
The DNA content of gametes (sex cells) is half that of somatic cells. In cases of polyploidy
(multiple sets of chromosomes) the DNA content increases by a proportional factor.
The mutagenic effect of UV light peaks at 253.7nm. This is the peak for the absorption of UV
light be DNA.
The Nucleic Acid Structure
Ribose and deoxyribose
These are pentose sugars. They have 5 carbons
The sugar-phosphate backbone of polynucleotides
The nucleotides are all orientated in the same direction.
The phosphate group joins the 3rd Carbon of
one sugar to the 5th Carbon of the next in
Adding in the bases
The bases are attached to the 1st Carbon.
Their order is important. It determines the genetic information of the molecule.
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