Structure of dna and rna and their difference

1. MICROBIAL GENETICS
TOPIC : STRUCTURE OF DNA & RNA AND
THEIR DIFFERENCE
SUBMITTED BY : D S SRIMATHI
Bsc MICROBIOLOGY
REFERENCE : NET REFERENCE

2. THE STRUCTURE OF DNA
Deoxyribonucleic Acid (DNA) organic chemical of complex
molecular structure that is found in prokaryotic and eukaryotic cells and in
many viruses. DNA from any cell is a long rope like molecule composed of two
strands each wound around the other to form a double helix .The model for this
structure was first proposed by WATSON AND FRANCIS CRICK in 1953.when they
published an article entitled “ A STRUCTURE FOR DEOXYRIBONUCLEICACID”.They
received the nobel prize for these studies in 1962 .Each strand of the DNA helix
is made up of nucleotides linked together to form a chain a polynucleotide.
Each nucleotide is constructed of three parts :
A heterocyclic ( with more than one kind of atom ) ring of carbon and
nitrogen atom called a nitrogenous bases which is either purine or a
pyrimidine.
A 5 carbon sugar (pentose) called deoxyribose
A phosphoric acid.
In DNA two kinds of purines - adenine and guanine
And two kinds pyrimidines - cytosine and thymine

3. These four kinds of nucleotides are joined together in the polynucleotide
strands of DNA by phosphodiester linkages. One strand is held to another by
hydrogen bonds between the bases; the sequencing of this bonding is specific—
i.e., adenine bonds only with thymine, and cytosine only with guanine.
DNA stores biological information. The two strands of DNA run in
oppositedirections to each other and are thus antiparallel. The configuration of
the DNA molecule is highly stable, allowing it to act as a template for the
replication of new DNA molecules, as well as for the production (transcription)
of the related RNA(ribonucleic acid) molecule. A segment of DNA that codes
for the cell’s synthesis of a specific protein’s called a gene
Within a cell, DNA is organized into dense protein-DNA complexes
called chromosomes
 In eukaryotes, the chromosomes are located in the nucleus, although
DNA also is found in mitochondria and chloroplasts
 In prokaryotes, which do not have a membrane-bound nucleus, the
DNA is found as a single circular chromosome in the cytoplasm.
Some prokaryotes, such as bacteria, and a few eukaryotes have extra
chromosomal DNA known as plasmids.
RNA STRUCTURE
RNA is typically single stranded and is made of ribonucleotides that are
linked by phosphodiester bonds. A ribonucleotide in the RNA chain contains
ribose (the pentose sugar), one of the four nitrogenous bases (A, U, G, and C),
and a phosphate group. The subtle structural difference between the sugars
gives DNA added stability, making DNA more suitable for storage of genetic
information, whereas the relative instability of RNA makes it more suitable for
its more short-term functions. The RNA-specific pyrimidine uracil forms a
complementary base pair with adenine and is used instead of the thymine used
in DNA

4. FUNCTION OF RNA IN PROTEIN SYSTHESIS
Cells access the information stored in DNA by creating RNA to direct the
synthesis of proteins through the process of translation. Proteins within a cell
have many functions, including building cellular structures and serving as
enzyme catalysts for cellular chemical reactions that give cells their specific
characteristics.
TYPES OF RNA
There are three major types of RNA which occur in all organisms. They are
messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).
mRNA
The mRNA carries the message from the DNA, which controls all of the
cellular activities in a cell. If a cell requires a certain protein to be synthesized,
the gene for this product is “turned on” and the mRNA is synthesized through
the process of transcription ( RNA Transcription).
rRNA
Ribosomal RNA (rRNA) associates with a set of proteins to form
ribosomes. Ribosomes are composed of rRNA and protein
tRNA
Transfer RNA is also known as soluble RNA (sRNA). The tRNA is a small
molecule compared with other types of RNAs. The tRNA molecule performs a
number of functions. The most important one is to act as a carrier of aminoacid
to the site of protein synthesis.

5. DIFFERENCE : DNA AND RNA
DNA RNA
Deoxyribonucleicacid (DNA) Ribonuclecic acid (RNA)
DNA is a double-stranded molecule RNA is a single-stranded molecule
DNA is located in the chromosome
• Only inside the nucleus
RNA is located in the ribosome
• Inside, as well as outside the
nucleus
PURINES :
 Guanine and Adenine
PYRAMIDINE :
 Thymine and cytosine
PURINES :
 Guanine and Adenine
PYRAMIDINE :
 Uracil and cytosine
Long chain of nucleotides Short chain of nucleotides
Structural Features : B forms Structural Features : A forms
Function: Long term storage of
genetic material
Function : Used to transfer the genetic
code from the nucleus to the ribosomes
to make proteins.
Propagation : DNA is self-
replicating
Propagation: RNA is synthesized
from DNA as-needed basis.
Stability of DNA is high Stability of RNA is low