Introduction to Biology and the Processes of Science
CHAPTER NOTES
Learning Objectives
1. Structure, functions, and type of DNA
2. Watson and Crick’s Structural Model of DNA
3. Chemical Composition of DNA
4. Replication of DNA
5. Recombinant of DNA
INTRODUCTION
Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) the principal genetic materials of
living organisms are chemically called nucleic acids. Nucleic acid especially the DNA, a
universal genetic material of most of the organisms, is having all the features required to be a
good genetic materials.
DNA is a macromolecule and is a helically twisted double chain of poly deoxyribonucleotides. In
prokaryotes it occurs in nucleoid and also as plasmids, both are double stranded circular DNA. In
Eukaryotes most of the DNA is found in chromatin of nucleus. It is linear. Some small
quantitative of DNA are found in mitochondria and plastids which is generally double stranded
and circular RNA also acts as genetic material in majority of plant viruses.
Functions of DNA
1. Genetic material is able to store information used to control both the development and
metabolic activities of cell.
2. It should be chemically stable so that it can be replicated accurately during cell division.
3. It should be transmitted for generations.
4. It should be able to undergo mutations providing genetic variability required for
evolution.
STRUCTURE OF DNA
, Nucleic acid (DNA or RNA) first called nuclein by a Swiss chemist Friedreich Miescher (1869)
as he removed nuclei from pus cells and isolated DNA i.e., “nuclein” from it. Nucleic acid (DNA
or RNA) are macromolecules composed of repeating sub unit called nucleotides.
Constitution Of A Nucleotide
1. A phosphate group.
2. A five-carbon sugar (ribose in RNA and deoxydine in DNA)
3. A cyclic nitrogen containing compound called a base (purines and pyrimidines).
Most commonly DNA occurs as a double helix. The two spiral strands of DNA are collectively
called DNA duplex. Two separate and anti parallel chains of DNA are wound around each other
in a right handed helical manner grooves major and minor with the sugar phosphate backbone on
the outer sides. The bases paired by hydrogen bonding are stocked on each other. A five carbon
sugar (ribose in RNA and deoxyribose in DNA) A cyclic nitrogen containing compound called a
base ( purines and pyrimidines).
Most commonly DNA occurs as a double helix. The two spiral strands of DNA are collectively
called DNA duplex. Two separate and anti parallel chains of DNA are wound around each other
right-handed helical manner. The DNA double helix comes to have two types of alternate
grooves major and minor with the sugar phosphate backbone on the outer sides. The base paired
by hydrogen bonding are stocked on each other.
CHEMICAL COMPOSITION OF DNA
Deoxyribonucleotides (monomer) of DNA are composed by three different types of chemicals.
1. Phosphoric acid (H3PO4) has three reactive (-OH) groups of which two are involved in
forming sugar phosphate back bone of DNA.
2. Pentose sugar (C5H10O4) - DNA contains 2’-deoxy-D-ribose, hence the name
deoxyribose.
3. Nitrogen bases- DNA contains four different nitrogen bases (A, G, C & T). These four
bases are grouped in to two classes on the basis their chemical structure.
a. Purine base – Adenine and Guanine
b. Pyrimidine bases- Cytocine and uracil
4. Purine bases - DNA has two types of purines (adenine and guanine). Each purine is a type
of nitrogen base having a double ring structure (i.e. 9 member double rings with nitrogen
at 1, 3, 7 and 9 positions).
CHAPTER NOTES
Learning Objectives
1. Structure, functions, and type of DNA
2. Watson and Crick’s Structural Model of DNA
3. Chemical Composition of DNA
4. Replication of DNA
5. Recombinant of DNA
INTRODUCTION
Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) the principal genetic materials of
living organisms are chemically called nucleic acids. Nucleic acid especially the DNA, a
universal genetic material of most of the organisms, is having all the features required to be a
good genetic materials.
DNA is a macromolecule and is a helically twisted double chain of poly deoxyribonucleotides. In
prokaryotes it occurs in nucleoid and also as plasmids, both are double stranded circular DNA. In
Eukaryotes most of the DNA is found in chromatin of nucleus. It is linear. Some small
quantitative of DNA are found in mitochondria and plastids which is generally double stranded
and circular RNA also acts as genetic material in majority of plant viruses.
Functions of DNA
1. Genetic material is able to store information used to control both the development and
metabolic activities of cell.
2. It should be chemically stable so that it can be replicated accurately during cell division.
3. It should be transmitted for generations.
4. It should be able to undergo mutations providing genetic variability required for
evolution.
STRUCTURE OF DNA
, Nucleic acid (DNA or RNA) first called nuclein by a Swiss chemist Friedreich Miescher (1869)
as he removed nuclei from pus cells and isolated DNA i.e., “nuclein” from it. Nucleic acid (DNA
or RNA) are macromolecules composed of repeating sub unit called nucleotides.
Constitution Of A Nucleotide
1. A phosphate group.
2. A five-carbon sugar (ribose in RNA and deoxydine in DNA)
3. A cyclic nitrogen containing compound called a base (purines and pyrimidines).
Most commonly DNA occurs as a double helix. The two spiral strands of DNA are collectively
called DNA duplex. Two separate and anti parallel chains of DNA are wound around each other
in a right handed helical manner grooves major and minor with the sugar phosphate backbone on
the outer sides. The bases paired by hydrogen bonding are stocked on each other. A five carbon
sugar (ribose in RNA and deoxyribose in DNA) A cyclic nitrogen containing compound called a
base ( purines and pyrimidines).
Most commonly DNA occurs as a double helix. The two spiral strands of DNA are collectively
called DNA duplex. Two separate and anti parallel chains of DNA are wound around each other
right-handed helical manner. The DNA double helix comes to have two types of alternate
grooves major and minor with the sugar phosphate backbone on the outer sides. The base paired
by hydrogen bonding are stocked on each other.
CHEMICAL COMPOSITION OF DNA
Deoxyribonucleotides (monomer) of DNA are composed by three different types of chemicals.
1. Phosphoric acid (H3PO4) has three reactive (-OH) groups of which two are involved in
forming sugar phosphate back bone of DNA.
2. Pentose sugar (C5H10O4) - DNA contains 2’-deoxy-D-ribose, hence the name
deoxyribose.
3. Nitrogen bases- DNA contains four different nitrogen bases (A, G, C & T). These four
bases are grouped in to two classes on the basis their chemical structure.
a. Purine base – Adenine and Guanine
b. Pyrimidine bases- Cytocine and uracil
4. Purine bases - DNA has two types of purines (adenine and guanine). Each purine is a type
of nitrogen base having a double ring structure (i.e. 9 member double rings with nitrogen
at 1, 3, 7 and 9 positions).
