Download stucture of DNA

1-Introduction
 George Mendel settled since one century that the biological
characteristics are inherited and he formulated a set of rules to
explain that inheritance.
 It was proposed that genes that are resided on chromosomes made
from proteins and they are responsible for genetic materials.
 Later on, techniques for gene mapping were developed and had
produced a comprehensive analysis of the relative positions of over
2000 genes on the four chromosomes of the fruit fly, Drosophila
melanogaster.
 The discovery that genetic information is coded along the length of
a polymeric molecules composed of only four types of monomeric
units was one of the major scientific achievements of this century.
 This polymeric molecules, DNA, is the chemical basis of heredity
and is organized into genes, the fundamental units of genetic
information.
 Genes control the synthesis of various types of RNA, most of
which are involved in protein synthesis.
 Genes replication and function are controlled by feedback loops as
fig. 1
 DNA is found in close association with proteins forming
nucleoproteins.
2- Genetic Materials of the cell
- Avery and his colleagues 1944……… DNA is the
genetic information's.
- Genetic information of rough capsule could be
transferred from pneumococcus to smooth one by
transfer of the DNA.
- Hershey and Chase used radioactive bacteriophage by
labeling the outer protein with 35S and the inner DNA
with
32
P.
- When the bacteriophage infect the bacterial cells only
the DNA will inter the cell and replicate inside the cell
and the new phages arise contain labeled DNA with
32
P
from the parental DNA.
3- Nucleoproteins
- Nucleoproteins is the most important proteins of the
cells.
- Nucleoproteins under the effect of Pepsin…….Protein+
insoluble nuclein.
- Insoluble nuclein under the effect of Trypsin…….
Nucleic acid + simple protein
- The simple protein principally Histones and protamies.
- The basic amino acid are rich in arginine and histidine.
- Nucleoproteins is the large part of the nucleus and
present in ribosomes.
- The chromatin material is mainly Nucleoproteins
4- Components Of Nucleic Acids
- Nucleic acid consists of long chain of nucleotides attached
together by phosphate diester linkages.
- Each Nucleotide consists of three molecules; phosphoric group
(P), pentose sugar (C ) and one Nitrogenous base.
- The phosphate diester bond is between the phosphate group of
one nucleotide and the pentose sugar of the previous
nucleotide.
- There are two types of nucleic acids:
- 1- Ribonucleic acid………RNA
- 2- Deoxyribonucleic acid……..DNA
- They differ from each other in the types of pentose sugar and
nitrogenous bases.
- Pentose sugar (D-ribose in RNA)…(D-2-Deoxyribose in
DNA).
Nitrogenous bases:
They are Purine or Pyrimidine bases:
1- Pyrimidine bases:
- The pyrimidine ring is heterocyclic ring that contains four
carbon atoms and two nitrogen atoms.
- There are three types: a- cytosine (2- oxy-4-aminopyrimidine).
B- thymine(2,4-dioxy-5-methyl pyrimidine). C- uracil (2,4dioxypyrimidine).
2- Purine bases:
- The purine ring is heterocyclic ring composed of pyrimidine
ring fused to imidazole ring.
- There are two major purines, adenine (6-aminopurine) and
guanine (2-amino-6-oxypurine).
Structure of Nucleosides
- Nucleosides are composed of a purine or a pyrimidine base to
which a sugar (D-ribose D-2-Deoxyribose) is attached in Blinkage at N9 or N1, respectively. Figure 3 ‫انظري الجدول من فضلك‬
Structure of Nucleotides
- They are Nucleosides +Phosphate groups at one or more
hydroxyl groups of the pentose sugar.
- The phosphate group is attached to C3 of Ribose in RNA,
While its attached to C5 in DNA.
- DNA is a polymer of thymidylic acid, Deoxy cytidylic acid,
deoxy adenylic acid and deoxy guanylic acid. While RNA is a
polymer of Uridylate , Cytidilate, adenylate and guanylate.