This presentation show the experimental evidence of DNA is genetic material as well as different types of DNA and RNA.

1. GENETIC
MATERIAL
SUBMITTED BY:
AMRITANSHU PATHAK
M.Sc. BIOTECHNOLOGY, 1ST YEAR
DEPARTMENT OF BIOTECHNOLOGY, C.C.S. UNIVERSITY, MEERUT

2. CONTENT
INTRODUCTION
EXPERIMENTAL EVIDENCES
STRUCTURES
TYPES
DIFFERENCE BETWEEN

3. INTRODUCTION
Genetic material is a cellular material that plays a fundamental role in
determining the structure and nature of cell substances, and is capable of
self-propagating and variation. The genetic material of a cell can be a gene,
a part of a gene, a group of genes, a DNA or RNA molecule, a fragment of
DNA , a group of DNA molecules, or the entire genome of an organism. It
can be found in the nucleus, mitochondria, and cytoplasm, depending on the
type of organism, i.e. if it is a prokaryote or eukaryote.
The genetic material controls the organism’s composition and it is identical
in the somatic cells of a multicellular organism. The genetic material has the
ability to replicate with the cell so new cells contain the same genetic
material as the parent cell.

4. EXPERIMENTAL EVIDENCES
By the early 1900’s, biochemists had isolated hundreds of different chemicals from living cells. However, a few
key experiments demonstrated that DNA, rather than protein, is the genetic material.
Griffith’s Transformation
Experiment (1928-30)
• They identified two strains of the bacterium Streptococcus pneumoniae. The R-strain produced rough
colonies on a bacterial plate, while the other S-strain was smooth (Fig: 1).
• More importantly, the S-strain bacteria caused fatal infections when injected into mice, while the R-strain did
not. Neither did “heat-treated” S-strain cells.
• Griffith in 1929 noticed that upon mixing “heat-treated” S-strain cells together with some R-type bacteria
(neither should kill the mice), the mice died and there were S-strain, pathogenic cells recoverable.
• Thus, some non-living component from the S-type strains contained genetic information that could be
transferred to and transform the living R-type strain cells into S-type cells.

6. Avery, MacLeod and McCarty’s
Experiment (1944)
• Researchers named Avery, MacLeod and McCarty separated the S-type cells into various components, such
as proteins, polysaccharides, lipids, and nucleic acids.
• Only the nucleic acids from S-type cells were able to make the R-strains smooth and fatal. Furthermore,
when cellular extracts of S-type cells were treated with DNase (an enzyme that digests DNA), the
transformation ability was lost.
• The researchers therefore concluded “that DNA was the genetic material”, which in this case controlled the
appearance (smooth or rough) and pathogenicity of the bacteria.

8. Hershey and Chase’s Experiment
(1952)
• Further evidence that DNA is the genetic material came from experiments
conducted by Hershey and Chase. These researchers studied the
transmission of genetic information in a virus called the T2
bacteriophage, which used Escherichia coli as its host bacterium.
• To determine which of these two types of molecules contained the genetic
blueprint for the virus, Hershey and Chase grew viral cultures in the
presence of radioactive isotopes of either phosphorus (32P) or sulphur
(35S). The phage incorporated these isotopes into their DNA and proteins.
• After ensuring that all viruses had been removed from the surface of the
cells, the researchers observed that infection with 32P labeled viruses (but
not the 35S labeled viruses) resulted in radioactive bacteria. This
demonstrated that DNA was the material that contained genetic
instructions.

10. STRUCTURE
• In and
discovered the structure of
DNA.
• The works of Rosalind Franklin lead
to Watson and Crick’s discovery.
Franklin first had pointed out that
the DNA is made up of two spirals.
• DNA is a double-stranded helix.
That is each DNA molecule is
comprised of two biopolymer
strands coiling around each other to
form a double helix structure.
• The shape of the helix is stabilized
by hydroGen bonding and
hydrophobic interactions between
bases.
• The diameter of double helix is 2nm
and the double helical structure
repeats at an interval of 3.4nm which
corresponds to ten base pairs.
B-DNA

11. Z- DNA A- DNA

12. • The discovery of RNA began with the discovery of
nucleic acids by Friedrich Miescher in 1868 who called
the material 'nuclein' since it was found in the nucleus.
• Ribonucleic acid (RNA) is a molecule that is present in
the majority of living organisms and viruses.
• It is made up of nucleotides, which are ribose sugars
attached to nitrogenous bases and phosphate groups. The
nitrogenous bases include adenine, guanine, uracil, and
cytosine.
• RNA mostly exists in the single-stranded form, but there
are special RNA viruses that are double-stranded. The
RNA molecule can have a variety of lengths and
structures.
• Three main types of RNA are involved in protein
synthesis. They are messenger RNA (mRNA), transfer
RNA (tRNA), and ribosomal RNA (rRNA).

13. transfer RNA (tRNA)
• Transfer ribonucleic acid (tRNA) is a
type of RNA molecule that helps decode
a messenger RNA (mRNA) sequence
into a protein.
• tRNAs function at specific sites in the
ribosome during translation, which is a
process that synthesizes a protein from
an mRNA molecule.
• Each codon represents a particular
amino acid, and each codon is
recognized by a specific tRNA.
• The tRNA molecule has a distinctive
folded structure with three hairpin loops
that form the shape of a three-leafed
clover.

14. messenger RNA (mRNA)
• So mRNA really is a form of nucleic acid, which
helps the human genome which is coded in DNA
to be read by the cellular machinery. mRNA is
created during transcription.
• During the transcription process, a single strand
of DNA is decoded by RNA polymerase, and
mRNA is synthesized. Physically, mRNA is a
strand of nucleotides known as ribonucleic acid,
and is single-stranded.
ribosomal RNA (rRNA).
• Ribosomal ribonucleic acid (rRNA) is the
RNA component of ribosomes, the molecular
machines that catalyze protein synthesis.
• Ribosomal RNA constitute over sixty percent
of the ribosome by weight and are crucial for
all its functions – from binding to mRNA and
recruiting tRNA to catalyzing the formation of
a peptide bond between two amino acids.

15. Main Differences Between DNA and RNA
Comparison DNA RNA
Name DeoxyriboNucleic Acid RiboNucleic Acid
Function
Long-term storage of genetic information;
transmission of genetic information to make
other cells and new organisms.
Used to transfer the genetic code
from the nucleus to the ribosomes
to make proteins. RNA is used to
transmit genetic information in
some organisms and may have been
the molecule used to store genetic
blueprints in primitive organisms.
Structural Features
B-form double helix. DNA is a double-stranded
molecule consisting of a long chain of
nucleotides.
A-form helix. RNA usually is a
single-strand helix consisting of
shorter chains of nucleotides.
Propagation DNA is self-replicating.
RNA is synthesized from DNA on
an as-needed basis.
Ultraviolet Damage DNA is susceptible to UV damage
Compared with DNA, RNA is
relatively resistant to UV damage